FixedTimeStartWith

warning off by default quick-fix

Group: Performance · PhpStorm name: FixedTimeStartWithInspection

strpos($s, 'lit') === 0 scans the whole haystack when the prefix is absent, so its cost grows with the length of $s. Comparing only the first N bytes with strncmp/strncasecmp answers the same "starts with" question in time bounded by the needle length.

Example

Before

<?php
function prefixes($url, $head, $part)
{
    return [
        strpos($url, 'https') === 0,
        0 !== stripos($head, 'Accept:'),
        \strpos($url, 'C:\\') !== 0,
        0 === strpos($url, 'it\'s'),

        strpos($url, 'https') == 0,
        strpos($url, 'https', 2) === 0,
        strpos($url, $part) === 0,
        strpos($url, "{$part}/") === 0,
        (strpos($url, 'https')) === 0,
        strpos($url, 'https') === false,
        strpos($url, '') === 0,
    ];
}

After fix

<?php
function prefixes($url, $head, $part)
{
    return [
        strncmp($url, 'https', 5) === 0,
        0 !== strncasecmp($head, 'Accept:', 7),
        \strncmp($url, 'C:\\', 3) !== 0,
        0 === strncmp($url, 'it\'s', 4),

        strpos($url, 'https') == 0,
        strpos($url, 'https', 2) === 0,
        strpos($url, $part) === 0,
        strpos($url, "{$part}/") === 0,
        (strpos($url, 'https')) === 0,
        strpos($url, 'https') === false,
        strpos($url, '') === 0,
    ];
}

Reported:

• line 5: Use 'strncmp($url, 'https', 5)' for a length-independent prefix check.
• line 6: Use 'strncasecmp($head, 'Accept:', 7)' for a length-independent prefix check.
• line 7: Use '\strncmp($url, 'C:\\', 3)' for a length-independent prefix check.
• line 8: Use 'strncmp($url, 'it\'s', 4)' for a length-independent prefix check.

Configure

In custos.json:

{
  "rules": {
    "FixedTimeStartWith": {
      "enabled": true
    }
  }
}

Suppress

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

// @custos-ignore FixedTimeStartWith

/**
 * @noinspection FixedTimeStartWithInspection
 */