![]() ![]() The second allows for an alternative value if a falsy one is regarded as insufficient. I have often used it in situations where null or false indicate failure. ![]() The first example, often seen in PERL, could have been written as but reads a little more naturally. This has the benefit of allowing some simple constructions such as: By design, OR is evaluated after assignment (while || is evaluated before assignment). This is about its usefulness.īoth OR and || are short-circuited operators, which means they will stop evaluating once they reach a TRUE value. $index = array_search ( $element, $array ) Ī previous comment notes the trap you can fall into with this operator. ![]() So you have to explicitly check for FALSE, otherwise you'll probably loose some elements:įunction remove_element ( $element, $array ) The problem here is, although array_search returns boolean false when it doesn't find specific element, it is interpreted as zero when used as array index. Just something that will probably save time for many new developers: beware of interpreting FALSE and TRUE as integers.įor example, a small function for deleting elements of an array may give unexpected results if you are not fully aware of what happens: This is why you should NEVER use the OR operator without explicit parentheses around the expression where it is being used. $z will be TRUE, as expected, because the || operator has higher precedence than assignment: The code is equivalent to $z=($y OR $x). On the other hand, after this code sequence: In this case, $z will be FALSE because the above code is equivalent to rather than as might be expected - because the OR operator has lower precedence than assignment operators. Speaking of GOTCHAs, consider this code sequence: Instead, there's another GOTCHA for the less-than-completely-experienced programmer to watch out for, and fixing the language's design error at this late date would undoubtedly break so many things that the correction is completely out of the question. The *correct* design would have been that *any* non-empty string is TRUE - period, end of story. ![]() Why? If *any* non-empty strings are going to be considered FALSE, why *only* a single zero? Why not "FALSE" (preferably case insensitive), or "0.0" (with how many decimal places), or "NO" (again, case insensitive), or. PHP's handling of strings as booleans is *almost* correct - an empty string is FALSE, and a non-empty string is TRUE - with one exception: A string containing a single zero is considered FALSE. It appears there's a lot more truth in this universe, but false can trump anything that's true. Now that we have 64 bit compilers using an int variable for booleans, there is *one* value which is FALSE (zero) and 2**64-1 values that are TRUE (everything else). Getting Started Introduction A simple tutorial Language Reference Basic syntax Types Variables Constants Expressions Operators Control Structures Functions Classes and Objects Namespaces Enumerations Errors Exceptions Fibers Generators Attributes References Explained Predefined Variables Predefined Exceptions Predefined Interfaces and Classes Predefined Attributes Context options and parameters Supported Protocols and Wrappers Security Introduction General considerations Installed as CGI binary Installed as an Apache module Session Security Filesystem Security Database Security Error Reporting User Submitted Data Hiding PHP Keeping Current Features HTTP authentication with PHP Cookies Sessions Dealing with XForms Handling file uploads Using remote files Connection handling Persistent Database Connections Command line usage Garbage Collection DTrace Dynamic Tracing Function Reference Affecting PHP's Behaviour Audio Formats Manipulation Authentication Services Command Line Specific Extensions Compression and Archive Extensions Cryptography Extensions Database Extensions Date and Time Related Extensions File System Related Extensions Human Language and Character Encoding Support Image Processing and Generation Mail Related Extensions Mathematical Extensions Non-Text MIME Output Process Control Extensions Other Basic Extensions Other Services Search Engine Extensions Server Specific Extensions Session Extensions Text Processing Variable and Type Related Extensions Web Services Windows Only Extensions XML Manipulation GUI Extensions Keyboard Shortcuts ? This help j Next menu item k Previous menu item g p Previous man page g n Next man page G Scroll to bottom g g Scroll to top g h Goto homepage g s Goto searchĪh, yes, booleans - bit values that are either set (TRUE) or not set (FALSE). ![]()
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