Problems and solutions when using in_array function in PHP

First introduce the demand background:

Invoice method:

0=Donation (don’t ask me why, historical reasons)

1=Send in the center

2=Request

3=Electronic invoice

Now we need to match The data submitted by the user is tested:

php;auto-links:false;">if(!in_array($_POST['invoice_action'], array(0,1,2,3))){
  throw new Exception('请选择正确的发票方式');
}

A problem arises at this time. If the value $_POST['invoice_action'] does not exist at all, why is no exception thrown?

After confirmation, this is what PHP does A pitfall of weakly typed languages, yes, this is a pit.

Look at this set of code:

echo in_array('', array(0)) ? 1 : 0;   // 结果：1
echo in_array(null, array(0)) ? 1 : 0;  // 结果：1
echo in_array(false, array(0)) ? 1 : 0; // 结果：1

Such a big pit, how do we bypass or fill it?

Method 1: in_array supports the third parameter, forcing data type detection

echo in_array('', array(0), true) ? 1 : 0;   // 结果：0
echo in_array(null, array(0), true) ? 1 : 0;  // 结果：0
echo in_array(false, array(0), true) ? 1 : 0; // 结果：0

Method 2: Still in the data type direction, change the 0 in the array to a string

echo in_array('', array('0'), true) ? 1 : 0;   // 结果：0
echo in_array(null, array('0'), true) ? 1 : 0;  // 结果：0
echo in_array(false, array('0'), true) ? 1 : 0; // 结果：0

Summary

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