Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
Disable APC auto recompile modified PHP files
Answer:
If you want extra performance boost for PHP/APC, you can tell APC not to auto recompile modified PHP files even they have changed. This can save APC for not to check the modification time of your script on every request.
To do so, edit your php.ini, and add
apc.apc.stat = 0
Restart your web server (e.g. Apache) to take effect.
How to check if a function exists in PHP?
Answer:
You can use the function_exists to check if a function exists in PHP before calling it.
E.g.
<?php
if ( function_exists("my_function") ) {
my_function();
}
Strict comparison in PHP
Answer:
PHP has two ways to compare two variables, type-safe and type-less, e.g.
Type-safe
print ( "123" === "123" ); // print 1
print ( 123 === 123 ); // print 1
print ( 123 === "123" ); // print nothing
Type-less
print ( "123" == "123" ); // print 1
print ( 123 == 123 ); // print 1
print ( 123 == "123" ); // print 1
Reference: http://php.net/manual/en/language.operators.comparison.php
Floating point precision in PHP
Answer:
It is typical that simple decimal fractions like 0.1 or 0.7 cannot be converted into their internal binary counterparts without a small loss of precision. This can lead to confusing results: for example, floor((0.1+0.7)*10) will usually return 7 instead of the expected 8, since the internal representation will be something like 7.9.
E.g.
$a = 0.1;
$b = 0.7;
print $a + $b;
print (( $a + $b ) * 10);
Reference: http://www.php.net/manual/en/language.types.float.php
So, never compare two floating numbers in your program.
Faster string length testing in PHP
Answer:
If you want to ensure a string variable has a particular length, you might use strlen
if ( strlen($str) > 10 ) {
// ...
}
A faster approach is to use isset
if ( isset($str[10]) ) {
// ...
}
