substr_compare

(PHP 5, PHP 7, PHP 8)

substr_compare — Comparar dos strings desde un offset hasta una longitud en caracteres

Descripción

substr_compare(
    string $haystack,
    string $needle,
    int $offset,
    ?int $length = null,
    bool $case_insensitive = false
): int

substr_compare() compara haystack desde la posición offset con needle durante length caracteres.

Parámetros

haystack: El string principal a comparar.
needle: El string secundario a comparar.
offset: La posición de inicio para la comparación. Si es un valor negativo, se comienza a contar desde el final del string.
length: La longitud de la comparación. El valor por omisión es el máximo entre la longitud de needle y la longitud de haystack menos el parámetro offset.
case_insensitive: Si case_insensitive vale true, la comparación no distingue entre mayúsculas y minúsculas.

Valores devueltos

Returns a value less than 0 if string1 is less than string2; a value greater than 0 if string1 is greater than string2, and 0 if they are equal. No particular meaning can be reliably inferred from the value aside from its sign.

Si length es igual (anterior a PHP 7.2.18, 7.3.5) o mayor que el tamaño de haystack o que length está definido y es inferior a 0, substr_compare() muestra una alerta y retorna false.

Historial de cambios

Versión	Descripción
8.2.0	This function is no longer guaranteed to return `strlen($string1) - strlen($string2)` when string lengths are not equal, but may now return `-1` or `1` instead.
8.0.0	`length` ahora es nullable.
7.2.18, 7.3.5	`offset` ahora puede ser igual al tamaño de `haystack`.

Ejemplos

Ejemplo #1 Ejemplo con substr_compare()

<?php
echo substr_compare("abcde", "bc", 1, 2), PHP_EOL; // 0
echo substr_compare("abcde", "de", -2, 2), PHP_EOL; // 0
echo substr_compare("abcde", "bcg", 1, 2), PHP_EOL; // 0
echo substr_compare("abcde", "BC", 1, 2, true), PHP_EOL; // 0
echo substr_compare("abcde", "bc", 1, 3), PHP_EOL; // 1
echo substr_compare("abcde", "cd", 1, 2), PHP_EOL; // -1
echo substr_compare("abcde", "abc", 5, 1), PHP_EOL; // -1
?>

Ver también

strncmp() - Comparación binaria de los n primeros caracteres

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User Contributed Notes 3 notes

down

jimmetry at gmail dot com ¶

12 years ago

When you came to this page, you may have been looking for something a little simpler: A function that can check if a small string exists within a larger string starting at a particular index. Using substr_compare() for this can leave your code messy, because you need to check that your string is long enough (to avoid the warning), manually specify the length of the short string, and like many of the string functions, perform an integer comparison to answer a true/false question.

I put together a simple function to return true if $str exists within $mainStr. If $loc is specified, the $str must begin at that index. If not, the entire $mainStr will be searched.

<?php

function contains_substr($mainStr, $str, $loc = false) {
    if ($loc === false) return (strpos($mainStr, $str) !== false);
    if (strlen($mainStr) < strlen($str)) return false;
    if (($loc + strlen($str)) > strlen($mainStr)) return false;
    return (strcmp(substr($mainStr, $loc, strlen($str)), $str) == 0);
}

?>

down

bishop at php dot net ¶

8 years ago

This function efficiently implements checks for strings beginning or ending with other strings:

<?php

function str_begins($haystack, $needle) {
  return 0 === substr_compare($haystack, $needle, 0, strlen($needle));
}

function str_ends($haystack,  $needle) {
  return 0 === substr_compare($haystack, $needle, -strlen($needle));
}

var_dump(str_begins('http://example.com', 'https://'));

?>

Note that these are not multi-byte character set aware.

down

Skyborne ¶

12 years ago

Take note of the `length` parameter: "The default value is the largest of the length of the str compared to the length of main_str less the offset."

This is *not* the length of str as you might (I always) expect, so if you leave it out, you'll get unexpected results.  Example:

<?php
$hash = '$5$lalalalalalalala$crypt.output.here';
var_dump(substr_compare($hash, '$5$', 0)); # int(34)
var_dump(substr_compare($hash, '$5$', 0, 3)); # int(0)
var_dump(PHP_VERSION); # string(6) "5.3.14"
?>

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