I just learned php and don't understand what this code means

I just learned php. what does this code mean? These two pieces of code should be judged. It should be placed in the judgment statement, but the author of the code does not. what does it mean? In_array ($ in, $ file) ===false & amp; exit ;! Ini_get ('safe _ mode' I just learned php and don't understand what this code means?
These two pieces of code should be judged. It should be placed in the judgment statement, but the author of the code does not. what does it mean?

In_array ($ in, $ file) ===false & exit;
! Ini_get ('safe _ mode') & set_time_limit (0 );

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In_array ($ in, $ file) ===false & exit;
If & the preceding condition is met, the following expression is executed, which is equivalent
If (in_array ($ in, $ file) === false ){
Exit;
}
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Upstairs.
! Ini_get ('safe _ mode') & set_time_limit (0 );
Check whether the security module is enabled in the PHP configuration file and whether the script running time is set to infinite (unlimited time)
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In fact, a more reasonable explanation is:
Expression 1 & expression 2
If expression 1 returns true, expression 2 is executed. if expression 2 returns true, true is returned.
When expression 1 returns false, expression 2 does not need to be executed.
If (expression 1 & expression 2) so that you can understand its process
| Relationship of "yes", that is, whether or not the two values are checked to be true or not. if either of them is true, true is returned.