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Logical Operators & Strings

Logical Operators & Strings

In this lesson we will look at how to use logical operators and strings in PHP.

Logical Operators

Use of the || “or” comparison operator is discouraged, as its clarity on some output devices is low (looking like the number 11, for instance). && is preferred over AND but either are acceptable, and space should always precede and follow !.

Example: Incorrect

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if ($foo || $bar)
if ($foo AND $bar)  // okay but not recommended for common syntax highlighting applications
if (!$foo)
if (! is_array($foo))

Example: Correct

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if ($foo OR $bar)
if ($foo && $bar) // recommended
if ( ! $foo)
if ( ! is_array($foo))

Strings

Always use single quoted strings unless you need variables parsed, and in cases where you do need variables parsed, use braces to prevent greedy token parsing. You may also use double-quoted strings if the string contains single quotes, so you do not have to use escape characters.

Example: Incorrect

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"My String"                                     // no variable parsing, so no use for double quotes
"My string $foo"                                // needs braces
'SELECT foo FROM bar WHERE baz = \'bag\''       // ugly

Example: Correct

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'My String'
"My string {$foo}"
"SELECT foo FROM bar WHERE baz = 'bag'"