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Digg  is_scalar
Finds whether a variable is a scalar
(PHP 4 >= 4.0.5, PHP 5)
Example 2594. is_scalar() example<?phpThe above example will output: 3.1416Code Examples / Notes » is_scalardocey
just a warning as it appears that an empty value is not a scalar. although the manual says scalars are: -> integers (eg. 243) -> floats (eg. 14.4) -> strings (eg "this is a string") -> booleans (eg true or false) this might seem easy but rembere that empty values are: -> NULL -> false -> empty string -> 0 -> "0" thus the true list of scalars must be: -> integers large then zero -> floats larger then zero -> strings with a lenght large then zero -> string that do not contain only the number 0 -> boolean value of true. especialy the boolean value false can be tricky as true is considerd to be scalar but false is not. or a string that is initialized with a zero lenght here's an example. $string = ""; //initialize our string. function store_var($var) { if(is_scalar($var)){ print("our var is a scalar."); }else{ print("you tried to store something else here."); } } $this->store_var($string); // does not work as expected this might be usefull when you create method to store a variable inside a class but do not want to store other stuff like object, arrays or resources, but storing an empy value is oke. then is_scalar does not work as empty values are incorrectly not seens as a bool, string, integer or float. this is an important downside to is_scalar wich might cause some people to loose there hair from headscrachting. this might be added to the manual as a warning or something. bps7j
is_scalar(null) is false. Apparently a variable needs to have a value to be considered a scalar.
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Hi ... for newbees here, I just want to mention that reference and scalar variable aren't the same. A reference is a pointer to a scalar, just like in C or C++. <? php // simple reference to scalar $a = 2; $ref = & $a; echo "$a $ref"; ?> this should print out: "2 2". Scalar class also exists. Look below: <? php class Object_t { var $a; function Object_t () // constructor { $this->a = 1; } } $a = new Object_t; // we define a scalar object $ref_a = &a; echo "$a->a $ref->a"; ?> again, this should echo: "1 1"; Here is another method isued in OOP to acheive on working only over reference to scalar object. Using this, you won't ever have to ask yourself if you work on a copy of the scalar or its reference. You will only possess reference to the scalar object. If you want to duplicate the scalar object, you will have to create a function for that purpose that would read by the reference the values and assign them to another scalar of the same type... or an other type, it is as you wish at that moment. <?php class objet_t { var $a; function object_t { $this->a = "patate_poil"; } } function &get_ref($object_type) { // here we create a scalar object in memory // and we return it by reference to the calling // control scope. return &new $object_type; } $ref_object_t = get_ref(object_t); echo "$ref_object_t->a "; ?> this should echo: "patate_poit ". The only thing that I try to demonstrate is that scalar variable ARE object in memory while a reference is usualy a variable (scalar object) that contain the address of another scalar object, which contain the informations you want by using the reference. Good Luck! otek is popanowel HAT hotmailZ DOT cum dr k
Having hunted around the manual, I've not found a clear statement of what makes a type "scalar" (e.g. if some future version of the language introduces a new kind of type, what criterion will decide if it's "scalar"? - that goes beyond just listing what's scalar in the current version.) In other lanuages, it means "has ordering operators" - i.e. "less than" and friends. It (-:currently:-) appears to have the same meaning in PHP. 31-jul-2006 04:59
Another warning in response to the previous note: > just a warning as it appears that an empty value is not a scalar. That statement is wrong--or, at least, has been fixed with a later revision than the one tested. The following code generated the following output on PHP 4.3.9. CODE: <?php echo('is_scalar() test:'.EOL); echo("NULL: " . print_R(is_scalar(NULL), true) . EOL); echo("false: " . print_R(is_scalar(false), true) . EOL); echo("(empty): " . print_R(is_scalar(''), true) . EOL); echo("0: " . print_R(is_scalar(0), true) . EOL); echo("'0': " . print_R(is_scalar('0'), true) . EOL); ?> OUTPUT: is_scalar() test: NULL: false: 1 (empty): 1 0: 1 '0': 1 THUS: * NULL is NOT a scalar * false, (empty string), 0, and "0" ARE scalars efelch
A scalar is a single item or value, compared to things like arrays and objects which have multiple values. This tends to be the standard definition of the word in terms of programming. An integer, character, etc are scalars. Strings are probably considered scalars since they only hold "one" value (the value represented by the characters represented) and nothing else.
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debug_zval_dump doubleval empty floatval get_defined_vars get_resource_type gettype import_request_variables intval is_array is_binary is_bool is_buffer is_callable is_double is_float is_int is_integer is_long is_null is_numeric is_object is_real is_resource is_scalar is_string is_unicode isset print_r serialize settype strval unserialize unset var_dump var_export |
