checking memory_limit in PHP

Question

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

Answer 1

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.

Answer 2

Checking on command line:

php -i | grep "memory_limit"

Answer 3

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');                     

Answer 4

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;
}

Answer 5

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'));

Answer 6

Try to convert the value first (eg: 64M -> 64 * 1024 * 1024). After that, do comparison and print the result.

<?php
$memory_limit = ini_get('memory_limit');
if (preg_match('/^(\d+)(.)$/', $memory_limit, $matches)) {
    if ($matches[2] == 'M') {
        $memory_limit = $matches[1] * 1024 * 1024; // nnnM -> nnn MB
    } else if ($matches[2] == 'K') {
        $memory_limit = $matches[1] * 1024; // nnnK -> nnn KB
    }
}

$ok = ($memory_limit >= 64 * 1024 * 1024); // at least 64M?

echo '<phpmem>';
echo '<val>' . $memory_limit . '</val>';
echo '<ok>' . ($ok ? 1 : 0) . '</ok>';
echo '</phpmem>';

Please note that the above code is just an idea. Don't forget to handle -1 (no memory limit), integer-only value (value in bytes), G (value in gigabytes), k/m/g (value in kilobytes, megabytes, gigabytes because shorthand is case-insensitive), etc.