这是正确的顺序

Question

基本上我在$text var：

中存储了以下文本

$text = 'An airplane accelerates down a runway at 3.20 m/s2 for 32.8 s until is finally lifts off the ground. Determine the distance traveled before takeoff'.

我有一个函数用一个名为$replacements的数组取代文本中的一些关键字，这是（我对它做了一个var_dump）：

'm' => string 'meter' (length=5)
'meters' => string 'meter' (length=5)
's' => string 'second' (length=6)
'seconds' => string 'second' (length=6)
'n' => string 'newton' (length=6)
'newtons' => string 'newton' (length=6)
'v' => string 'volt' (length=4)
'speed' => string 'velocity' (length=8)
'\/' => string 'per' (length=3)
's2' => string 'secondsquare' (length=12)

该文本通过以下功能：

$toreplace = array_keys($replacements);

foreach ($toreplace as $r){
    $text = preg_replace("/\b$r\b/u", $replacements[$r], $text);
}

然而，我期望与输出之间存在差异：

Expected Output : an airplane accelerates down runway at 3.20 meterpersecondsquare for 32.8 second until finally lifts off ground determine distance traveled before takeoff 

Function Output : an airplane accelerates down runway at 3.20 meterpers2 for 32.8 second until finally lifts off ground determine distance traveled before takeoff

请注意，我希望'meterpersecondsquare'并且我得到'meterpers2'（'s2'未被替换），而'm'和'/'被替换为它们的值。

我注意到当我把m / s而不是m / s2时，它工作正常并给出：

an airplane accelerates down runway at 3.20 meterpersecond for 32.8 second until finally lifts off ground determine distance traveled before takeoff

所以问题基本上与s2不匹配。有什么想法是这样的吗？

Answer 1

在s2替换之前移动s替换。

由于您正在进行一次替换，因此在有机会替换它之前，您正在销毁s2。

3.20 m / s2 将会像这样转换

[m] 3.20米/秒

[s] 3.20米/秒2

[/] 3.20 meterpersecond2

这导致 meterpersecond2

这是正确的顺序

'm' => string 'meter' (length=5)
'meters' => string 'meter' (length=5)
's2' => string 'secondsquare' (length=12)
's' => string 'second' (length=6)
'seconds' => string 'second' (length=6)
'n' => string 'newton' (length=6)
'newtons' => string 'newton' (length=6)
'v' => string 'volt' (length=4)
'speed' => string 'velocity' (length=8)
'\/' => string 'per' (length=3)

Preg_replace无法正常工作

1 个答案:

这是正确的顺序