Questions tagged [php]
PHP is an open-source, multi-paradigm, dynamically-typed, and interpreted scripting language designed initially for server-side web development. Use this tag for questions about programming in the PHP language.
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Reference Guide: What does this symbol mean in PHP? (PHP Syntax)
What is this?
This is a collection of questions that come up now and then about syntax in PHP. This is also a Community Wiki, so everyone is invited to participate in maintaining this list.
Why is ...
3065
votes
27
answers
3.8m
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Deleting an element from an array in PHP
Is there an easy way to delete an element from an array using PHP, such that foreach ($array) no longer includes that element?
I thought that setting it to null would do it, but apparently it does ...
- 67.7k
2801
votes
31
answers
2.0m
views
How do I get a YouTube video thumbnail from the YouTube API?
If I have a YouTube video URL, is there any way to use PHP and cURL to get the associated thumbnail from the YouTube API?
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2773
votes
27
answers
2.2m
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How can I prevent SQL injection in PHP?
If user input is inserted without modification into an SQL query, then the application becomes vulnerable to SQL injection, like in the following example:
$unsafe_variable = $_POST['user_input'];
...
2720
votes
14
answers
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views
Why shouldn't I use mysql_* functions in PHP?
What are the technical reasons for why one shouldn't use mysql_* functions? (e.g. mysql_query(), mysql_connect() or mysql_real_escape_string())?
Why should I use something else even if they work on ...
- 174k
2657
votes
36
answers
6.7m
views
How do I check if a string contains a specific word?
Consider:
$a = 'How are you?';
if ($a contains 'are')
echo 'true';
Suppose I have the code above, what is the correct way to write the statement if ($a contains 'are')?
2312
votes
32
answers
476k
views
How do you parse and process HTML/XML in PHP?
How can one parse HTML/XML and extract information from it?
2278
votes
7
answers
458k
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How does PHP 'foreach' actually work?
Let me prefix this by saying that I know what foreach is, does and how to use it. This question concerns how it works under the bonnet, and I don't want any answers along the lines of "this is how you ...
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24
answers
833k
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When should I use 'self' over '$this'?
In PHP 5, what is the difference between using self and $this?
When is each appropriate?
- 52.1k
2000
votes
27
answers
3.5m
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How do I get PHP errors to display?
I have checked my PHP ini file (php.ini) and display_errors is set and also error reporting is E_ALL. I have restarted my Apache webserver.
I have even put these lines at the top of my script, and it ...
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votes
30
answers
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How Can I add HTML And CSS Into PDF [closed]
I have an HTML (not XHTML) document that renders fine in Firefox 3 and IE 7. It uses fairly basic CSS to style it and renders fine in HTML.
I'm now after a way of converting it to PDF. I have tried:...
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37
answers
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startsWith() and endsWith() functions in PHP
How can I write two functions that would take a string and return if it starts with the specified character/string or ends with it?
For example:
$str = '|apples}';
echo startsWith($str, '|'); //...
- 265k
1568
votes
34
answers
3.8m
views
How do I make a redirect in PHP?
Is it possible to redirect a user to a different page through the use of PHP?
Say the user goes to www.example.com/page.php and I want to redirect them to www.example.com/index.php, how would I do so ...
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1440
votes
28
answers
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Difference between require, include, require_once and include_once?
In PHP:
When should I use require vs. include?
When should I use require_once vs. include_once?
- 39.5k
1434
votes
37
answers
2.2m
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How to get the client IP address in PHP
How can I get the client IP address using PHP?
I want to keep record of the user who logged into my website through his/her IP address.
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1403
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17
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1.2m
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How to Sort a Multi-dimensional Array by Value
How can I sort this array by the value of the "order" key?
Even though the values are currently sequential, they will not always be.
Array
(
[0] => Array
(
[...
- 27.2k
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votes
29
answers
2.2m
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"Notice: Undefined variable", "Notice: Undefined index", "Warning: Undefined array key", and "Notice: Undefined offset" using PHP
I'm running a PHP script and continue to receive errors like:
Notice: Undefined variable: my_variable_name in C:\wamp\www\mypath\index.php on line 10
Notice: Undefined index: my_index C:\wamp\www\...
1358
votes
13
answers
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UTF-8 all the way through
I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.
Where ...
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1337
votes
11
answers
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How do you use bcrypt for hashing passwords in PHP? [duplicate]
Every now and then I hear the advice "Use bcrypt for storing passwords in PHP, bcrypt rules".
But what is bcrypt? PHP doesn't offer any such functions, Wikipedia babbles about a file-encryption ...
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1332
votes
39
answers
2.1m
views
Get the first element of an array
I have an array:
array( 4 => 'apple', 7 => 'orange', 13 => 'plum' )
I would like to get the first element of this array. Expected result: string apple
One requirement: it cannot be ...
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1317
votes
40
answers
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Enumerations on PHP
I know that PHP doesn't yet have native Enumerations. But I have become accustomed to them from the Java world. I would love to use enums as a way to give predefined values which IDEs' auto-completion ...
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1283
votes
39
answers
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Reference - What does this error mean in PHP?
What is this?
This is a number of answers about warnings, errors, and notices you might encounter while programming PHP and have no clue how to fix them. This is also a Community Wiki, so everyone is ...
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15
answers
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How can I sanitize user input with PHP?
Is there a catchall function somewhere that works well for sanitizing user input for SQL injection and XSS attacks, while still allowing certain types of HTML tags?
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14
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Secure hash and salt for PHP passwords
It is currently said that MD5 is partially unsafe. Taking this into consideration, I'd like to know which mechanism to use for password protection.
This question, Is “double hashing” a password less ...
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4
answers
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What are Long-Polling, Websockets, Server-Sent Events (SSE) and Comet?
I have tried reading some articles, but I am not very clear on the concepts yet.
Would someone like to take a shot at explaining to me what these technologies are:
Long Polling
Server-Sent Events
...
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1176
votes
18
answers
1.2m
views
How do I expire a PHP session after 30 minutes?
I need to keep a session alive for 30 minutes and then destroy it.
- 34k
1165
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18
answers
673k
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1164
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21
answers
1.3m
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PHP array delete by value (not key)
I have a PHP array like so:
$messages = [312, 401, 1599, 3, ...];
Given that the values in the array are unique, how can I delete the element with a given value (without knowing its key)?
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1139
votes
16
answers
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What is the difference between public, private, and protected?
When and why should I use public, private, and protected functions and variables inside a class? What is the difference between them?
Examples:
// Public
public $variable;
public function ...
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20
answers
1.6m
views
Returning JSON from a PHP Script
I want to return JSON from a PHP script.
Do I just echo the result? Do I have to set the Content-Type header?
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18
answers
1.5m
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How do I use PHP to get the current year?
I want to put a copyright notice in the footer of a web site, but I think it's incredibly tacky for the year to be outdated.
How would I make the year update automatically with PHP
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votes
14
answers
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Detecting request type in PHP (GET, POST, PUT or DELETE)
How can I detect which request type was used (GET, POST, PUT or DELETE) in PHP?
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1083
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14
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1.2m
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Where can I find php.ini?
Today I needed to install the IBM DB2 library. I went through all the steps up to make install, and I found ibm_db2.so in $PHP_HOME/lib/extensions/somecomplicatedname/ibm_db2.so.
The great catch is ...
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45
answers
3.2m
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How do I get the current date and time in PHP?
Which PHP function can return the current date/time?
Mike
1046
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27
answers
1.4m
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Remove empty array elements
Some elements in my array are empty strings from users. $linksArray still has empty elements after the following:
foreach($linksArray as $link)
{
if($link == '')
{
unset($link);
}
}...
- 11k
1016
votes
69
answers
1.8m
views
PHP random string generator
I'm trying to create a randomized string in PHP, and I get absolutely no output with this:
<?php
function RandomString()
{
$characters = '...
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1006
votes
32
answers
1.9m
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Convert a PHP object to an associative array
I'm integrating an API to my website which works with data stored in objects while my code is written using arrays.
I'd like a quick-and-dirty function to convert an object to an array.
- 37k
1005
votes
31
answers
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mysql_fetch_array()/mysql_fetch_assoc()/mysql_fetch_row()/mysql_num_rows etc... expects parameter 1 to be resource
I am trying to select data from a MySQL table, but I get one of the following error messages:
mysql_fetch_array() expects parameter 1 to be resource, boolean given
This is my code:
$username = $...
- 24.9k
975
votes
27
answers
4.0m
views
Get the full URL in PHP
I use this code to get the full URL:
$actual_link = 'http://'.$_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF'];
The problem is that I use some masks in my .htaccess, so what we see in the URL is not ...
- 45.5k
941
votes
36
answers
2.9m
views
How do I convert a string to a number in PHP?
I want to convert these types of values, '3', '2.34', '0.234343', etc. to a number. In JavaScript we can use Number(), but is there any similar method available in PHP?
Input Output
'2' ...
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941
votes
5
answers
462k
views
What is thread safe or non-thread safe in PHP?
I saw different binaries for PHP, like non-thread or thread safe?
What does this mean?
What is the difference between these packages?
- 11.1k
932
votes
7
answers
476k
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What is the difference between single-quoted and double-quoted strings in PHP?
I'm a little confused why I see some code in PHP with string placed in single quotes and sometimes in double quotes.
I just know in .NET, or the C language, if it is in a single quote, that means it ...
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924
votes
60
answers
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How to check if PHP array is associative or sequential?
PHP treats all arrays as associative, so there aren't any built in functions. Can anyone recommend a fairly efficient way to check if an array "is a list" (contains only numeric keys ...
865
votes
32
answers
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views
How can I get a file's extension in PHP?
This is a question you can read everywhere on the web with various answers:
$ext = end(explode('.', $filename));
$ext = substr(strrchr($filename, '.'), 1);
$ext = substr($filename, strrpos($filename, '...
- 587k
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votes
38
answers
1.3m
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How do I get the query builder to output its raw SQL query as a string?
Given the following code:
DB::table('users')->get();
I want to get the raw SQL query string that the database query builder above will generate. In this example, it would be SELECT * FROM users.
...
- 11.4k
831
votes
16
answers
2.0m
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How to fix "Headers already sent" error in PHP
When running my script, I am getting several errors like this:
Warning: Cannot modify header information - headers already sent by (output started at /some/file.php:12) in /some/file.php on line 23
...
830
votes
7
answers
1.2m
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Remove trailing delimiting character from a delimited string
What is fastest way to remove the last character from a string?
I have a string like
a,b,c,d,e,
I would like to remove the last ',' and get the remaining string back:
OUTPUT: a,b,c,d,e
What is ...
- 15.8k
823
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33
answers
1.1m
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How to calculate the difference between two dates using PHP?
I have two dates of the form:
Start Date: 2007-03-24
End Date: 2009-06-26
Now I need to find the difference between these two in the following form:
2 years, 3 months and 2 days
How can I do this ...
gnanesh
822
votes
25
answers
655k
views
Get first key in a (possibly) associative array?
What's the best way to determine the first key in a possibly associative array? My first thought it to just foreach the array and then immediately breaking it, like this:
foreach ($an_array as $key =&...
- 25.5k
809
votes
17
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How do I implement basic "Long Polling"?
I can find lots of information on how Long Polling works (For example, this, and this), but no simple examples of how to implement this in code.
All I can find is cometd, which relies on the Dojo JS ...
- 168k