PHP code version dependency

Question

This question was migrated from Webmasters Stack Exchange because it can be answered on Stack Overflow. Migrated 6 years ago.

In each and every version of php, some new features are added and some features are stopped.

Example:

<?php
$hex = hex2bin("6578616d706c65206865782064617461");
var_dump($hex);
?>

will need php 5.4.0 and above, as hex2bin was introduced in php 5.4.0.
It is tedious to check version dependency manually in php.net for each and every built-in functions used in php code. Is there any automated/semi-automated way to identify the minimum version (and maximum version if applicable) of php installation would be needed to execute any given php code?

Answer 1

Check out the PHPCompatibility project : https://github.com/wimg/PHPCompatibility This tests your code for compatibility with 5.2, 5.3, 5.4 and 5.5(alpha2 at the time of writing)

Answer 2

Don't know if there is a way to check in php wich version is needed, but you could use "function_exists" to see if your version of php has that function.

http://php.net/manual/en/function.function-exists.php

<?php
if (function_exists('hex2bin')) {
    echo "hex2bin function is available.<br />\n";
} else {
    echo "hex2bin function is not available.<br />\n";
}
?>

Answer 3

It's up to the programmer to state the dependencies of his or her library / project.

Many projects now use Composer as a dependency manager, but for legacy code you can't do much but running it and swearing against errors.

Answer 4

Good practice could be to have fallbacks. Just like mentioned in this function, there are alternatives.

if ( ! function_exists('hex2bin')) {
    function hex2bin($hexstr)
    {
        $n = strlen($hexstr);
        $sbin="";  
        $i=0;
        while($i<$n)
        {      
            $a =substr($hexstr,$i,2);          
            $c = pack("H*",$a);
            if ($i==0){$sbin=$c;}
            else {$sbin.=$c;}
            $i+=2;
        }
        return $sbin;
    }
}

Code is based on Johnson's reply.

Setting essential function which does that same as new ones in case they don't exist lets you go about your business without having to fear incompability. Just hide these where you don't have any reason to edit them and they won't bother you either.

Answer 5

You can create a manual checking ,then using 'patch'.To define what is missing.

Using phpversion();

 if (strnatcmp(phpversion(),'5.2.10') >= 0) 
 { 
       //loading patch

 } 
 else 
 { 
     //loading patch
      function abc(){
        //
      }
 }