• Use single quotes for strings
o When you surround a PHP string in double quotes, it is subsequently parsed by the PHP interpreter for variables and special characters, such as "\n". If you just want to output a basic string, use single quotes! There is a marginal performance benefit, since the string does not get parsed.
o “print” is slower than “echo”, putting variables inline in a string is slower than concatenating them, and concatenating strings is slower than using comma-separated echo values! Not only does not-inlining your variables give you a performance boost, but it also makes your code easier to read in any editor that has syntax highlighting (your variables will show up in nice colors).
echo "Hi my name is ",$a,". I am ",$b; //Good
print "Hi my name is $a. I am $b"; //Bad
• Use single-quotes around array indexes
o PHP considers the unquoted index as a "bare" string, and considers it a defined constant. When it can't find a matching symbol for this constant in the symbol table however, it converts it to a real string, which is why your code will work. Quoting the index prevents this constant-checking stuff, and makes it safer in case someone defines a future constant with the same name.
$arr['name'] //Good
$arr[name] //Bad
• Don't use short open tags.It can cause conflicts with XML parsers, and if you ever distribute code, it's going to annoy the heck out of people who have to start modifying their PHP ini directives to get it to work.
• Don't use regular expressions if you don't need to.
o If you're doing basic string operations, stay away from the preg and ereg function groups whenever possible. str_replace is much faster than preg_replace, and strtr is even faster than str_replace.
• Don't use functions inside a loop declaration.
o If you use a function like count() inside a loop declaration, it's going to get executed at every iteration! If your loop is large, you're using a lot of extra execution time.
$count = count($array);
for($i = 0; $i < $count; $i++) {} //Good
for ($i = 0; $i < count($array); $i++) {} //Bad
• Never rely on register_globals or magic quotes.
• Always initialize your variables
o PHP will automatically create a variable if it hasn't been initialized, but it's not good practice to rely on this feature. It makes for sloppy code, and in large functions or projects can become quite confusing if you have to track down where it's being created. In addition, incrementing an uninitialized variable is much slower than if it was initialized.
• Validate and sanitize your inputs
o Always use isset() or empty() before checking for type because is_array() is costly and could waste many valuable cpu-cycles if the variable isn't even set in the first place. Short-circuit is your best friend when it comes to efficient programming.
if (isset($myVar) && is_array($myVar)) {} //Good
if ($myVar) { } //Bad
• It’s better to use switch case statements than multi if, else if, statements.
• Cache as much as possible. Use memcached - memcached is a high-performance memory object caching system intended to speed up dynamic web applications by alleviating database load. OP code caches are useful so that your script does not have to be compiled on every request.
• mod_gzip which is available as an Apache module compresses your data on the fly and can reduce the data to transfer up to 80%.
• Do NOT use SQL wildcard select. eg. SELECT *.
• Possibly use “strncasecmp”, “strpbrk” and “stripos” instead of “regex.”.
• Just declaring a global variable without using it in a function also slows things down (by about the same amount as incrementing a local var). PHP probably does a check to see if the global exists.
