How is the difference between false and 0 in php?

In PHP, when the variable is 0, the variable is "equal to" false "at the same time. How can we distinguish between 0 and false? This is useful in some condition statements. This article will give an example.

First, check the Code:

The function of this Code is to find whether a string starts with a word.

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$ Title = "Hello world ."; $ Keyword = "you "; If (strpos ($ title, $ keyword) = 0 ){ Echo "correct "; } Else { Echo "error "; } Output: Correct

It seems that the code is correct? Why is the result incorrect? View the help manual. When the strpos () function finds a word in a string, if the word exists, the index position of the word is returned. Otherwise, false is returned. The code is modified as follows.

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If (strpos ($ title, $ keyword) = 0 ){ Echo "correct "; } Else if (strpos ($ title, $ keyword) = false ){ Echo "error "; } Output: Correct

Why is it wrong? In PHP, when the variable is 0, the variable is "equal to" false "at the same time. How can we distinguish between 0 and false? In fact, it is very easy to modify the code:

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If (strpos ($ title, $ keyword) === 0 ){ Echo "correct "; } Else if (strpos ($ title, $ keyword) === false ){ Echo "error "; } Output: Error

Example

The Code is as follows:

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<? Php /* * Test boolean * 0 false */ $ Num = 0; $ BTest1 = false; $ BTest2 = true; $ StrTest2 = 'false '; If ($ num = $ bTest1) { Echo ('digits 0 and false are equal '); // display Echo ("<br/> "); } If ($ bTest1) { Echo ('never execute <br/> '); // not displayed } If (1) { Echo ('will it be executed? <br/>'); // Execute } If ($ bTest2) { Echo ('I am the boss, I want to execute <br/>'); // Execute } Else { Echo ('none of them belong to me. <br/> '); } Echo (false = 0); // 1 indicates equal Echo (true = 1); // display 1 to indicate equal Function testReturn () { Echo ('aaaaa '); Return; Return 'bbbbbb '; Echo ('cccccc '); } // Return indicates that the return of the function is not executed until it is executed, and exit is the launch program. Echo testReturn (); // call this function to output 'aaa' 'bbbbbbb' ?>

In many cases, false is equal to 0. When we want to return a value containing 0, for example, we need to pay attention to the number query. We can use ===to determine whether it is completely equal,

PHP has a gettype () function to obtain the variable type. You can use the = Operator (after reading it, there are three equal signs ). The difference between the = Operator and the = Operator is that the operator compares the values and types of data at the same time.
 
When different variable types are involved in the termination condition, use = and! = It is very important to perform a strong type check for operators.