php - 当模式涉及美元符号 ($) 时，正则表达式失败

Question

在匹配涉及美元符号的子模式时，我遇到了一些问题。例如，考虑以下文本 block :

Regular Price: $20.50       Final Price: $15.20
Regular Price: $18.99       Final Price: $2.25
Regular Price: $11.22       Final Price: $33.44
Regular Price: $55.66       Final Price: $77.88

我试图将常规/最终价格集与以下正则表达式相匹配，但它根本不起作用(根本没有匹配项):
preg_match_all("/正常价格:\$(\d+\.\d{2}).*最终价格:\$(\d+\.\d{2})/U", $data, $matches );

我逃脱了美元符号，那又如何呢？

Answer 1

Inside a double quoted string the backslash is treated as an escape character for the $. The backslash is removed by the PHP parser even before the preg_match_all function sees it:

$r = "/Regular Price: \$(\d+\.\d{2}).*Final Price: \$(\d+\.\d{2})/U";
var_dump($r);

输出(ideone):

"/Regular Price: $(\d+\.\d{2}).*Final Price: $(\d+\.\d{2})/U"                 ^                           ^              the backslashes are no longer there

To fix this use a single quoted string instead of a double quoted string:

preg_match_all('/Regular Price: \$(\d+\.\d{2}).*Final Price: \$(\d+\.\d{2})/U',
               $data,
               $matches);

在线查看:ideone