substr_compare

(PHP 5)

substr_compareBinary safe comparison of two strings from an offset, up to length characters

Description

int substr_compare ( string $main_str , string $str , int $offset [, int $length [, bool $case_insensitivity = false ]] )

substr_compare() compares main_str from position offset with str up to length characters.

Parameters

main_str

The main string being compared.

str

The secondary string being compared.

offset

The start position for the comparison. If negative, it starts counting from the end of the string.

length

The length of the comparison. The default value is the largest of the length of the str compared to the length of main_str less the offset.

case_insensitivity

If case_insensitivity is TRUE, comparison is case insensitive.

Return Values

Returns < 0 if main_str from position offset is less than str, > 0 if it is greater than str, and 0 if they are equal. If offset is equal to or greater than the length of main_str or length is set and is less than 1, substr_compare() prints a warning and returns FALSE.

Changelog

Version Description
5.1.0 Added the possibility to use a negative offset.

Examples

Example #1 A substr_compare() example

<?php
echo substr_compare("abcde""bc"12); // 0
echo substr_compare("abcde""de", -22); // 0
echo substr_compare("abcde""bcg"12); // 0
echo substr_compare("abcde""BC"12true); // 0
echo substr_compare("abcde""bc"13); // 1
echo substr_compare("abcde""cd"12); // -1
echo substr_compare("abcde""abc"51); // warning
?>

See Also

  • strncmp() - Binary safe string comparison of the first n characters

Коментарии

Автор:
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'$5$'03)); # int(0)
var_dump(PHP_VERSION); # string(6) "5.3.14"
?>
2012-08-03 16:55:30
http://php5.kiev.ua/manual/ru/function.substr-compare.html
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$locstrlen($str)), $str) == 0);
}

?>
2012-12-16 02:31:03
http://php5.kiev.ua/manual/ru/function.substr-compare.html
This function efficiently implements checks for strings beginning or ending with other strings:

<?php

function str_begins($haystack$needle) {
  return 
=== substr_compare($haystack$needle0strlen($needle));
}

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

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

?>

Note that these are not multi-byte character set aware.
2016-10-03 22:28:33
http://php5.kiev.ua/manual/ru/function.substr-compare.html

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