[php] checking memory_limit in PHP

I'm need to check if memory_limit is at least 64M in my script installer. This is just part of PHP code that should work, but probably due to this "M" it's not reading properly the value. How to fix this ?

  //memory_limit
    echo "<phpmem>";
    if(key_exists('PHP Core', $phpinfo))
    {
        if(key_exists('memory_limit', $phpinfo['PHP Core']))
        {
            $t=explode(".", $phpinfo['PHP Core']['memory_limit']);
            if($t[0]>=64)
                $ok=1;
            else
                $ok=0;
            echo "<val>{$phpinfo['PHP Core']['memory_limit']}</val><ok>$ok</ok>";
        }
        else
           echo "<val></val><ok>0</ok>";
    }
    else
        echo "<val></val><ok>0</ok>";
    echo "</phpmem>\n"; 

This question is related to php memory-limit

The answer is


Thank you for inspiration.

I had the same problem and instead of just copy-pasting some function from the Internet, I wrote an open source tool for it. Feel free to use it or provide feedback!

https://github.com/BrandEmbassy/php-memory

Just install it using Composer and then you get the current PHP memory limit like this:

$configuration = new \BrandEmbassy\Memory\MemoryConfiguration();
$limitProvider = new \BrandEmbassy\Memory\MemoryLimitProvider($configuration);
$limitInBytes = $memoryLimitProvider->getLimitInBytes();

Here is another simpler way to check that.

$memory_limit = return_bytes(ini_get('memory_limit'));
if ($memory_limit < (64 * 1024 * 1024)) {
    // Memory insufficient      
}

/**
* Converts shorthand memory notation value to bytes
* From http://php.net/manual/en/function.ini-get.php
*
* @param $val Memory size shorthand notation string
*/
function return_bytes($val) {
    $val = trim($val);
    $last = strtolower($val[strlen($val)-1]);
    $val = substr($val, 0, -1);
    switch($last) {
        // The 'G' modifier is available since PHP 5.1.0
        case 'g':
            $val *= 1024;
        case 'm':
            $val *= 1024;
        case 'k':
            $val *= 1024;
    }
    return $val;
}

Command line to check ini:

$ php -r "echo ini_get('memory_limit');"

very old post. but i'll just leave this here:

/* converts a number with byte unit (B / K / M / G) into an integer */
function unitToInt($s)
{
    return (int)preg_replace_callback('/(\-?\d+)(.?)/', function ($m) {
        return $m[1] * pow(1024, strpos('BKMG', $m[2]));
    }, strtoupper($s));
}

$mem_limit = unitToInt(ini_get('memory_limit'));

As long as your array $phpinfo['PHP Core']['memory_limit'] contains the value of memory_limit, it does work the following:

  • The last character of that value can signal the shorthand notation. If it's an invalid one, it's ignored.
  • The beginning of the string is converted to a number in PHP's own specific way: Whitespace ignored etc.
  • The text between the number and the shorthand notation (if any) is ignored.

Example:

# Memory Limit equal or higher than 64M?
$ok = (int) (bool) setting_to_bytes($phpinfo['PHP Core']['memory_limit']) >= 0x4000000;

/**
 * @param string $setting
 *
 * @return NULL|number
 */
function setting_to_bytes($setting)
{
    static $short = array('k' => 0x400,
                          'm' => 0x100000,
                          'g' => 0x40000000);

    $setting = (string)$setting;
    if (!($len = strlen($setting))) return NULL;
    $last    = strtolower($setting[$len - 1]);
    $numeric = (int) $setting;
    $numeric *= isset($short[$last]) ? $short[$last] : 1;
    return $numeric;
}

Details of the shorthand notation are outline in a PHP manual's FAQ entry and extreme details are part of Protocol of some PHP Memory Stretching Fun.

Take care if the setting is -1 PHP won't limit here, but the system does. So you need to decide how the installer treats that value.


Checking on command line:

php -i | grep "memory_limit"

Not so exact but simpler solution:

$limit = str_replace(array('G', 'M', 'K'), array('000000000', '000000', '000'), ini_get('memory_limit'));
if($limit < 500000000) ini_set('memory_limit', '500M');                     

If you are interested in CLI memory limit:

cat /etc/php/[7.0]/cli/php.ini | grep "memory_limit"

FPM / "Normal"

cat /etc/php/[7.0]/fpm/php.ini | grep "memory_limit"