SubStrShortHandUsage

warning on by default quick-fix

Group: Performance · PhpStorm name: SubStrShortHandUsageInspection

substr() / mb_substr() accept a negative length ("stop N characters before the end") and treat a missing length as "up to the end". Computing the length as strlen($s) - something is therefore either replaceable by a negative constant, or entirely unnecessary.

Example

Before

<?php
function cut($name, $head, $k) {
    $a = substr($name, 0, strlen($name) - 4);
    $b = mb_substr($name, 3, mb_strlen($name) - 5, 'UTF-8');
    $c = \substr($name, 7, strlen($name) - 2);
    $d = mb_substr($name, $k, mb_strlen($name) - $k);
    $e = mb_substr(
        $name,
        strlen($head),
        mb_strlen($name) - strlen($head),
        'UTF-8'
    );

    $f = substr($name, $k, strlen($name) - 1);
    $g = substr($name, 0, strlen($head) - 1);
    $h = substr($name, 0, (strlen($name) - 1));
    $i = substr($name, 0x1, strlen($name) - 2);
    $j = substr($name, 0, mb_strlen($name, 'UTF-8') - 1);
    $m = mb_substr($name, 0, strlen($name) - 2);
    return [$a, $b, $c, $d, $e, $f, $g, $h, $i, $j, $m];
}

After fix

<?php
function cut($name, $head, $k) {
    $a = substr($name, 0, -4);
    $b = mb_substr($name, 3, -2, 'UTF-8');
    $c = \substr($name, 7);
    $d = mb_substr($name, $k);
    $e = mb_substr(
        $name, strlen($head), null, 'UTF-8'
    );

    $f = substr($name, $k, strlen($name) - 1);
    $g = substr($name, 0, strlen($head) - 1);
    $h = substr($name, 0, (strlen($name) - 1));
    $i = substr($name, 0x1, strlen($name) - 2);
    $j = substr($name, 0, mb_strlen($name, 'UTF-8') - 1);
    $m = mb_substr($name, 0, strlen($name) - 2);
    return [$a, $b, $c, $d, $e, $f, $g, $h, $i, $j, $m];
}

Reported:

• line 3: Pass '-4' as the length instead.
• line 4: Pass '-2' as the length instead.
• line 5: The length 'strlen($name) - 2' is unnecessary; remove it.
• line 6: The length 'mb_strlen($name) - $k' is unnecessary; remove it.
• line 10: The length 'mb_strlen($name) - strlen($head)' is unnecessary; remove it.

Configure

In custos.json:

{
  "rules": {
    "SubStrShortHandUsage": {
      "enabled": false
    }
  }
}

Suppress

Before the statement or declaration (or the first statement of the file), either of:

// @custos-ignore SubStrShortHandUsage

/**
 * @noinspection SubStrShortHandUsageInspection
 */