正则表达式匹配一个确切的字符串

Question

使用PHP，什么是正则表达式匹配一个确切的字符串。

说我们有文字：

Hello, world. 

How are you today? 

Today is sunshine and snow wouldn't you know. 

我将如何使用正则表达式来匹配字符串？：

sunshine and snow 

Answer 1

使用的preg_match：

<?php 
// The "i" after the pattern delimiter indicates a case-insensitive search 
if (preg_match("/php/i", "PHP is the web scripting language of choice.")) { 
    echo "A match was found."; 
} else { 
    echo "A match was not found."; 
} 
?> 

使用strpos：

<?php 
$mystring = 'abc'; 
$findme = 'a'; 
$pos = strpos($mystring, $findme); 

// Note our use of ===. Simply == would not work as expected 
// because the position of 'a' was the 0th (first) character. 
if ($pos === false) { 
    echo "The string '$findme' was not found in the string '$mystring'"; 
} else { 
    echo "The string '$findme' was found in the string '$mystring'"; 
    echo " and exists at position $pos"; 
} 
?>