It's worth noting this function is surprisingly fast. I first ran it against a ~500KB string on our web server. It found 6 occurrences of the needle I was looking for in 0.0000 seconds. Yes, it ran faster than microtime() could measure.
Looking to give it a challenge, I then ran it on a Mac laptop from 2010 against a 120.5MB string. For one test needle, it found 2385 occurrences in 0.0266 seconds. Another test needs found 290 occurrences in 0.114 seconds.
Long story short, if you're wondering whether this function is slowing down your script, the answer is probably not.
substr_count
(PHP 4, PHP 5, PHP 7)
substr_count — Count the number of substring occurrences
설명
int substr_count
( string
$haystack
, string $needle
[, int $offset = 0
[, int $length
]] )
substr_count() returns the number of times the
needle substring occurs in the
haystack string. Please note that
needle is case sensitive.
Note:
This function doesn't count overlapped substrings. See the example below!
인수
-
haystack -
The string to search in
-
needle -
The substring to search for
-
offset -
The offset where to start counting. If the offset is negative, counting starts from the end of the string.
-
length -
The maximum length after the specified offset to search for the substring. It outputs a warning if the offset plus the length is greater than the
haystacklength. A negative length counts from the end ofhaystack.
반환값
This function returns an integer.
변경점
| 버전 | 설명 |
|---|---|
| 7.1.0 |
Support for negative offsets and lengths has been added.
|
| 5.1.0 |
Added the offset and
the length parameters
|
예제
Example #1 A substr_count() example
<?php
$text = 'This is a test';
echo strlen($text); // 14
echo substr_count($text, 'is'); // 2
// the string is reduced to 's is a test', so it prints 1
echo substr_count($text, 'is', 3);
// the text is reduced to 's i', so it prints 0
echo substr_count($text, 'is', 3, 3);
// generates a warning because 5+10 > 14
echo substr_count($text, 'is', 5, 10);
// prints only 1, because it doesn't count overlapped substrings
$text2 = 'gcdgcdgcd';
echo substr_count($text2, 'gcdgcd');
?>
참고
- count_chars() - 문자열 안에 사용한 문자에 대한 정보를 반환
- strpos() - 문자열이 처음 나타나는 위치를 찾습니다
- substr() - Return part of a string
- strstr() - 문자열이 처음으로 나오는 부분을 찾습니다
add a note
User Contributed Notes 10 notes
tuxedobob ¶
8 years ago
flobi at flobi dot com ¶
18 years ago
Making this case insensitive is easy for anyone who needs this. Simply convert the haystack and the needle to the same case (upper or lower).
substr_count(strtoupper($haystack), strtoupper($needle))
tweston at bangordailynews dot com ¶
9 years ago
To account for the case that jrhodes has pointed out, we can change the line to:
substr_count ( implode( ',', $haystackArray ), $needle );
This way:
array (
0 => "mystringth",
1 => "atislong"
);
Becomes
mystringth,atislong
Which brings the count for $needle = "that" to 0 again.
jrhodes at roket-enterprises dot com ¶
15 years ago
It was suggested to use
substr_count ( implode( $haystackArray ), $needle );
instead of the function described previously, however this has one flaw. For example this array:
array (
0 => "mystringth",
1 => "atislong"
);
If you are counting "that", the implode version will return 1, but the function previously described will return 0.
XinfoX X at X XkarlX X-X XphilippX X dot X XdeX ¶
21 years ago
Yet another reference to the "cgcgcgcgcgcgc" example posted by "chris at pecoraro dot net":
Your request can be fulfilled with the Perl compatible regular expressions and their lookahead and lookbehind features.
The example
$number_of_full_pattern = preg_match_all('/(cgc)/', "cgcgcgcgcgcgcg", $chunks);
works like the substr_count function. The variable $number_of_full_pattern has the value 3, because the default behavior of Perl compatible regular expressions is to consume the characters of the string subject that were matched by the (sub)pattern. That is, the pointer will be moved to the end of the matched substring.
But we can use the lookahead feature that disables the moving of the pointer:
$number_of_full_pattern = preg_match_all('/(cg(?=c))/', "cgcgcgcgcgcgcg", $chunks);
In this case the variable $number_of_full_pattern has the value 6.
Firstly a string "cg" will be matched and the pointer will be moved to the end of this string. Then the regular expression looks ahead whether a 'c' can be matched. Despite of the occurence of the character 'c' the pointer is not moved.
info at fat-fish dot co dot il ¶
17 years ago
a simple version for an array needle (multiply sub-strings):
<?php
function substr_count_array( $haystack, $needle ) {
$count = 0;
foreach ($needle as $substring) {
$count += substr_count( $haystack, $substring);
}
return $count;
}
?>
qeremy [atta] gmail [dotta] com ¶
11 years ago
Unicode example with "case-sensitive" option;
<?php
function substr_count_unicode($str, $substr, $caseSensitive = true, $offset = 0, $length = null) {
if ($offset) {
$str = substr_unicode($str, $offset, $length);
}
$pattern = $caseSensitive
? '~(?:'. preg_quote($substr) .')~u'
: '~(?:'. preg_quote($substr) .')~ui';
preg_match_all($pattern, $str, $matches);
return isset($matches[0]) ? count($matches[0]) : 0;
}
function substr_unicode($str, $start, $length = null) {
return join('', array_slice(
preg_split('~~u', $str, -1, PREG_SPLIT_NO_EMPTY), $start, $length));
}
$s = 'Ümit yüzüm gözüm...';
print substr_count_unicode($s, 'ü'); // 3
print substr_count_unicode($s, 'ü', false); // 4
print substr_count_unicode($s, 'ü', false, 10); // 1
print substr_count_unicode($s, 'üm'); // 2
print substr_count_unicode($s, 'üm', false); // 3
?>
php at blink dot at ¶
10 years ago
This will handle a string where it is unknown if comma or period are used as thousand or decimal separator. Only exception where this leads to a conflict is when there is only a single comma or period and 3 possible decimals (123.456 or 123,456). An optional parameter is passed to handle this case (assume thousands, assume decimal, decimal when period, decimal when comma). It assumes an input string in any of the formats listed below.
function toFloat($pString, $seperatorOnConflict="f")
{
$decSeperator=".";
$thSeperator="";
$pString=str_replace(" ", $thSeperator, $pString);
$firstPeriod=strpos($pString, ".");
$firstComma=strpos($pString, ",");
if($firstPeriod!==FALSE && $firstComma!==FALSE) {
if($firstPeriod<$firstComma) {
$pString=str_replace(".", $thSeperator, $pString);
$pString=str_replace(",", $decSeperator, $pString);
}
else {
$pString=str_replace(",", $thSeperator, $pString);
}
}
else if($firstPeriod!==FALSE || $firstComma!==FALSE) {
$seperator=$firstPeriod!==FALSE?".":",";
if(substr_count($pString, $seperator)==1) {
$lastPeriodOrComma=strpos($pString, $seperator);
if($lastPeriodOrComma==(strlen($pString)-4) && ($seperatorOnConflict!=$seperator && $seperatorOnConflict!="f")) {
$pString=str_replace($seperator, $thSeperator, $pString);
}
else {
$pString=str_replace($seperator, $decSeperator, $pString);
}
}
else {
$pString=str_replace($seperator, $thSeperator, $pString);
}
}
return(float)$pString;
}
function testFloatParsing() {
$floatvals = array(
"22 000",
"22,000",
"22.000",
"123 456",
"123,456",
"123.456",
"22 000,76",
"22.000,76",
"22,000.76",
"22000.76",
"22000,76",
"1.022.000,76",
"1,022,000.76",
"1,000,000",
"1.000.000",
"1022000.76",
"1022000,76",
"1022000",
"0.76",
"0,76",
"0.00",
"0,00",
"1.00",
"1,00",
"-22 000,76",
"-22.000,76",
"-22,000.76",
"-22 000",
"-22,000",
"-22.000",
"-22000.76",
"-22000,76",
"-1.022.000,76",
"-1,022,000.76",
"-1,000,000",
"-1.000.000",
"-1022000.76",
"-1022000,76",
"-1022000",
"-0.76",
"-0,76",
"-0.00",
"-0,00",
"-1.00",
"-1,00"
);
echo "<table>
<tr>
<th>String</th>
<th>thousands</th>
<th>fraction</th>
<th>dec. if period</th>
<th>dec. if comma</th>
</tr>";
foreach ($floatvals as $fval) {
echo "<tr>";
echo "<td>" . (string) $fval . "</td>";
echo "<td>" . (float) toFloat($fval, "") . "</td>";
echo "<td>" . (float) toFloat($fval, "f") . "</td>";
echo "<td>" . (float) toFloat($fval, ".") . "</td>";
echo "<td>" . (float) toFloat($fval, ",") . "</td>";
echo "</tr>";
}
echo "</table>";
}
gigi at phpmycoder dot com ¶
15 years ago
below was suggested a function for substr_count'ing an array, yet for a simpler procedure, use the following:
<?php
substr_count ( implode( $haystackArray ), $needle );
?>
chrisstocktonaz at gmail dot com ¶
15 years ago
In regards to anyone thinking of using code contributed by zmindster at gmail dot com
Please take careful consideration of possible edge cases with that regex, in example:
$url = 'http://w3.host.tld/path/to/file/..../file.extension';
$url = 'http://w3.host.tld/path/to/file/../file.extension?malicous=....';
This would cause a infinite loop and for example be a possible entry point for a denial of service attack. A correct fix would require additional code, a quick hack would be just adding a additional check, without clarity or performance in mind:
...
$i = 0;
while (substr_count($url, '../') && ++$i < strlen($url))
...
-Chris
