php计算子串在字符串中出现次数的函数substr_count()

<?php
echo substr_count("Hello world. The world is nice","world");
?>

substr_count(string,substring,start,length)

<?php
$str = "This is nice";
echo strlen($str)."<br>"; // Using strlen() to return the string length
echo substr_count($str,"is")."<br>"; // The number of times "is" occurs in the string
echo substr_count($str,"is",2)."<br>"; // The string is now reduced to "is is PHP"
echo substr_count($str,"is",3)."<br>"; // The string is now reduced to "s is PHP"
echo substr_count($str,"is",3,3)."<br>"; // The string is now reduced to "s i"
?>

<?php
$str = "abcabcab"; 
echo substr_count($str,"abcab"); // This function does not count overlapped substrings
?>

<?php
echo $str = "This is nice";
substr_count($str,"is",3,9);
?>

<?php
$text = 'This is a test';
echo strlen($text) . '<br />'; // 输出14
 
echo substr_count($text, 'is') . '<br />'; // 2
 
// the string is reduced to 's is a test', so it prints 1
echo substr_count($text, 'is', 3) . '<br />';//实际上就是从第四个字符开始查找是否在$text中含有is
 
// the text is reduced to 're ', so it prints 0
echo substr_count($text, 'are', 16, 3) . '<br />';
 
// the text is reduced to 's i', so it prints 0echo substr_count($text, 'is', 3, 3);
 
// generates a warning because 5+10 > 14
echo substr_count($text, 'is', 5, 10) . '<br />';
 
 
// prints only 1, because it doesn't count overlapped subtrings
$text2 = 'gcdgcdgcd';
echo substr_count($text2, 'gcdgcd') . '<br />';
 ?>