PHP 8 reference · String Functions

PHP strncmp() Function

Compare only the first n bytes of two strings, case-sensitively. Handy for checking a prefix in older code.

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Syntax

strncmp(string $string1, string $string2, int $length): int

0 if the first length bytes match; negative or positive otherwise.

Compare a prefixTry it yourself

<?php
var_dump(strncmp("ReadyCamel", "Ready", 5) === 0);
var_dump(strncmp("ReadyCamel", "ready", 5) === 0);

Output

bool(true)
bool(false)

Filter codesTry it yourself

<?php
foreach (["ERR-12", "OK-3", "ERR-7"] as $code) {
    if (strncmp($code, "ERR", 3) === 0) {
        echo $code, "\n";
    }
}

Output

ERR-12
ERR-7

Version	Change
PHP 4.0	Added

strcmp() · Compare two strings byte by byte, case-sensitively. Returns 0 when equal, less than 0 or more than 0 otherwise.
str_starts_with() · Check whether a string begins with a given substring. Case-sensitive and returns true or false; added in PHP 8.0.
PHP Strings · tutorial