douzhongjiu2263 2016-06-10 18:19
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如何跟踪变量值是否在同一个php while循环中多次使用

I found this snippet in a different question and answer, and it detects if a variable value is the same as the variable value in the previous loop.

$prevValue = NULL;
while(condition) {
 if ($curValue == $prevValue) {
  //do stuff
 }
 $prevValue = $curValue;
}

However what I want to do is to check if a variable value has been used before in the loop, but anywhere in the loop, so if the value happened 1 or 2 or 10 loops ago I want it to tell me if the variable value has come through the loop before.

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  • douchun6221 2016-06-10 18:22
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    Use an array to store each value and then check if the current value is in the array:

    $prevValues = array();
    while(/*condition*/) {
        if (in_array($curValue, $prevValues)) {
            //do stuff
        }
        $prevValues[] = $curValue;
    }
    

    As Marc B points out in a comment, you can do it this way as well. It might be marginally faster but I haven't tested it:

    while(/*condition*/) {
        if (isset($prevValues[$curValue])) {
            //do stuff
        }
        $prevValues[$curValue] = 1;  //set to whatever
    }
    
    本回答被题主选为最佳回答 , 对您是否有帮助呢?
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