PHP weak type safety issues

Notes on PHP weak type safety issues

1. Type conversion issues

intval();

 

    var_dump(intval('1asdfasd'));  //1

    var_dump(intval('awqw12'));  //0

    var_dump(intval(array()));    //0

    var_dump(intval(array('foo','val'))); //1

    var_dump(intval(0x1A)); //26  十六进制转换

    var_dump(intval('asdfqwer')); //0

intval If the value is converted to a string, an error will not be returned, but 0 will be returned. If the value is converted to an array, there are two situations. Convert the value When it is an empty array, it will return 0, otherwise it will return 1

Note: PHP uses 32-bit memory to save an integer. 32-bit can represent 4294967296 numbers. If it is signed, it is -2147483647 to 2147483648;

2. The problem of looseness of built-in functions

switch();
 
 
 
    $i='3adcd';
 
    switch($i){
 
             case 1:
 
                    echo 'i is 1';
 
                    break;
 
             case 2:
 
                    echo 'i is 2';
 
                    break;
 
             case 3:
 
                    echo 'i is 3';
 
                    break;
 
             default:
 
                   echo 'i is default';
 
                   break;
 
    }

The above results will enter switch case 3. Why is this? If switch is a numeric type case judgment, switch will convert the parameters into int class, so the above execution When, $i is first type-converted, and the conversion result is 3, so. . .

in_array();

    $arr = [0,1,2,3,'test'];

    var_dump(in_array('abd',$arr));    // true

    var_dump(in_array('1bc',$arr));    // true

Why is the above execution result like this? Later, through querying the manual, the official statement is that in_array defaults to a loose comparison method, which only compares whether the values ​​are equal, but does not compare whether the types of the values ​​are the same, so the above For this result, you can set the third parameter of the in_array function. Setting it to True is a strict comparison method.

The above are the things we need to pay attention to in our daily development.