1-point question about strtok in php

For some questions about strtok in php, please refer to the following code PHPcode & lt ;? Php $ string = & quot; Helloworld. beautifuldaytoday. & quot; $ token = strtok ($ string, & quot;); while ($ to some questions about strtok in php
See the following code

PHP code

  

  "; $ Token = strtok (" ") ;}?>

The condition for loop termination should be $ token = false, but strtok returns a value of the string type. how can the two be =?
It is known that ''= false is not true, that is, $ token ='' is also not true. what is the final value of $ token?

------ Solution --------------------
Php is a weak language. let's look at this example.

$ Str = '';

$ Token = strtok ($ str ,'');

Var_dump ($ token );

Bool (false) is returned at this time)

Have you seen it? So it is used! = FALSE;

------ Solution --------------------
Under normal circumstances, strtok does return a string, but it does not exist after finding the last one. at this time, the return value is not a string or NULL, but a boolean value of false, which is specified by the person who writes this function.