在PHP中正則表達式有一些問題

Question

：我如何在正則表達式中放置一個變量。

事情是這樣的：

$var = "Some text"; 
$regular_expression = '/\d.*h/' . $var . '/hw/'; 

謝謝！

Answer 1

這裏有兩種方法給一個變量寫入正則表達式模式的示範：

代碼：（Demo Link）

$string='8_hSome texthw 9_hSome texthw'; 
$var = "Some text"; 

//Single quoted pattern with dot-concatenation: 
$regex1= '/\d.*h' . $var . 'hw/'; 
var_export(preg_match_all($regex1,$string,$out)?$out:'failed'); 

echo "\n---\n"; 

// Double quoted pattern with curly bracketed variable isolation: 
$regex2= "/\d.*h{$var}hw/"; 
var_export(preg_match_all($regex2,$string,$out)?$out:'failed'); 

// note the greedy quantifier (*) matches 1 long substring, instead of two short substrings 

輸出：

array (
    0 => 
    array (
    0 => '8_hSome texthw 9_hSome texthw', 
), 
) 
--- 
array (
    0 => 
    array (
    0 => '8_hSome texthw 9_hSome texthw', 
), 
)