Php number characters string
Cast a string to binary using PHP < 5.2.1
I found it tricky to check if a posted value was an integer.
is_int ( $_POST [ ‘a’ ] ); //false
is_int ( intval ( «anything» ) ); //always true
?>
A method I use for checking if a string represents an integer value.
$foo [ ‘ten’ ] = 10 ; // $foo[‘ten’] is an array holding an integer at key «ten»
$str = » $foo [ ‘ten’]» ; // throws T_ENCAPSED_AND_WHITESPACE error
$str = » $foo [ ten ] » ; // works because constants are skipped in quotes
$fst = (string) $foo [ ‘ten’ ]; // works with clear intention
?>
It seems (unset) is pretty useless. But for people who like to make their code really compact (and probably unreadable). You can use it to use an variable and unset it on the same line:
$hello = ‘Hello world’ ;
print $hello ;
unset( $hello );
$hello = ‘Hello world’ ;
$hello = (unset) print $hello ;
?>
Hoorah, we lost another line!
It would be useful to know the precedence (for lack of a better word) for type juggling. This entry currently explains that «if either operand is a float, then both operands are evaluated as floats, and the result will be a float» but could (and I think should) provide a hierarchy that indicates, for instance, «between an int and a boolean, int wins; between a float and an int, float wins; between a string and a float, string wins» and so on (and don’t count on my example accurately capturing the true hierarchy, as I haven’t actually done the tests to figure it out). Thanks!
May be expected, but not stated ..
Casting to the existing (same) type has no effect.
$t = ‘abc’; // string ‘abc’
$u=(array) $t; // array 0 => string ‘abc’ $v=(array) $u; // array 0 => string ‘abc’
Correct me if I’m wrong, but that is not a cast, it might be useful sometimes, but the IDE will not reflect what’s really happening:
class MyObject /**
* @param MyObject $object
* @return MyObject
*/
static public function cast ( MyObject $object ) return $object ;
>
/** Does nothing */
function f () <>
>
class X extends MyObject /** Throws exception */
function f () < throw new exception (); >
>
$x = MyObject :: cast (new X );
$x -> f (); // Your IDE tells ‘f() Does nothing’
?>
However, when you run the script, you will get an exception.
In my much of my coding I have found it necessary to type-cast between objects of different class types.
More specifically, I often want to take information from a database, convert it into the class it was before it was inserted, then have the ability to call its class functions as well.
The following code is much shorter than some of the previous examples and seems to suit my purposes. It also makes use of some regular expression matching rather than string position, replacing, etc. It takes an object ($obj) of any type and casts it to an new type ($class_type). Note that the new class type must exist:
Looks like type-casting user-defined objects is a real pain, and ya gotta be nuttin’ less than a brain jus ta cypher-it. But since PHP supports OOP, you can add the capabilities right now. Start with any simple class.
class Point protected $x , $y ;
public function __construct ( $xVal = 0 , $yVal = 0 ) $this -> x = $xVal ;
$this -> y = $yVal ;
>
public function getX () < return $this ->x ; >
public function getY () < return $this ->y ; >
>
$p = new Point ( 25 , 35 );
echo $p -> getX (); // 25
echo $p -> getY (); // 35
?>
Ok, now we need extra powers. PHP gives us several options:
A. We can tag on extra properties on-the-fly using everyday PHP syntax.
$p->z = 45; // here, $p is still an object of type [Point] but gains no capability, and it’s on a per-instance basis, blah.
B. We can try type-casting it to a different type to access more functions.
$p = (SuperDuperPoint) $p; // if this is even allowed, I doubt it. But even if PHP lets this slide, the small amount of data Point holds would probably not be enough for the extra functions to work anyway. And we still need the class def + all extra data. We should have just instantiated a [SuperDuperPoint] object to begin with. and just like above, this only works on a per-instance basis.
C. Do it the right way using OOP — and just extend the Point class already.
class Point3D extends Point protected $z ; // add extra properties.
public function __construct ( $xVal = 0 , $yVal = 0 , $zVal = 0 ) parent :: __construct ( $xVal , $yVal );
$this -> z = $zVal ;
>
public function getZ () < return $this ->z ; > // add extra functions.
>
$p3d = new Point3D ( 25 , 35 , 45 ); // more data, more functions, more everything.
echo $p3d -> getX (); // 25
echo $p3d -> getY (); // 35
echo $p3d -> getZ (); // 45
?>
Once the new class definition is written, you can make as many Point3D objects as you want. Each of them will have more data and functions already built-in. This is much better than trying to beef-up any «single lesser object» on-the-fly, and it’s way easier to do.
Re: the typecasting between classes post below. fantastic, but slightly flawed. Any class name longer than 9 characters becomes a problem. SO here’s a simple fix:
function typecast($old_object, $new_classname) if(class_exists($new_classname)) // Example serialized object segment
// O:5:»field»:9: $old_serialized_prefix = «O:».strlen(get_class($old_object));
$old_serialized_prefix .= «:\»».get_class($old_object).»\»:»;
$old_serialized_object = serialize($old_object);
$new_serialized_object = ‘O:’.strlen($new_classname).’:»‘.$new_classname . ‘»:’;
$new_serialized_object .= substr($old_serialized_object,strlen($old_serialized_prefix));
return unserialize($new_serialized_object);
>
else
return false;
>
Thanks for the previous code. Set me in the right direction to solving my typecasting problem. 😉
If you have a boolean, performing increments on it won’t do anything despite it being 1. This is a case where you have to use a cast.
I have 1 bar.
I now have 1 bar.
I finally have 2 bar.
Checking for strings to be integers?
How about if a string is a float?
/* checks if a string is an integer with possible whitespace before and/or after, and also isolates the integer */
$isInt = preg_match ( ‘/^\s*(2+)\s*$/’ , $myString , $myInt );
echo ‘Is Integer? ‘ , ( $isInt ) ? ‘Yes: ‘ . $myInt [ 1 ] : ‘No’ , «\n» ;
/* checks if a string is an integer with no whitespace before or after */
$isInt = preg_match ( ‘/^2+$/’ , $myString );
echo ‘Is Integer? ‘ , ( $isInt ) ? ‘Yes’ : ‘No’ , «\n» ;
/* When checking for floats, we assume the possibility of no decimals needed. If you MUST require decimals (forcing the user to type 7.0 for example) replace the sequence:
8+(\.3+)?
with
5+\.8+
*/
/* checks if a string is a float with possible whitespace before and/or after, and also isolates the number */
$isFloat = preg_match ( ‘/^\s*(1+(\.4+)?)\s*$/’ , $myString , $myNum );
echo ‘Is Number? ‘ , ( $isFloat ) ? ‘Yes: ‘ . $myNum [ 1 ] : ‘No’ , «\n» ;
/* checks if a string is a float with no whitespace before or after */
$isInt = preg_match ( ‘/^5+(\.1+)?$/’ , $myString );
echo ‘Is Number? ‘ , ( $isFloat ) ? ‘Yes’ : ‘No’ , «\n» ;
Php number characters string
A PHP string is considered numeric if it can be interpreted as an int or a float .
WHITESPACES \s* LNUM 3+ DNUM (3*)[\.]) | ([\.]7*) EXPONENT_DNUM (( | ) [eE][+-]? ) INT_NUM_STRING [+-]? FLOAT_NUM_STRING [+-]? ( | ) NUM_STRING ( | )
PHP also has a concept of leading numeric strings. This is simply a string which starts like a numeric string followed by any characters.
Note:
Any string that contains the letter E (case insensitive) bounded by numbers will be seen as a number expressed in scientific notation. This can produce unexpected results.
var_dump ( «0D1» == «000» ); // false, «0D1» is not scientific notation
var_dump ( «0E1» == «000» ); // true, «0E1» is 0 * (10 ^ 1), or 0
var_dump ( «2E1» == «020» ); // true, «2E1» is 2 * (10 ^ 1), or 20
?>
Strings used in numeric contexts
- If the string is numeric, resolve to an int if the string is an integer numeric string and fits into the limits of the int type limits (as defined by PHP_INT_MAX ), otherwise resolve to a float .
- If the context allows leading numeric strings and the string is one, resolve to an int if the leading part of the string is an integer numeric string and fits into the limits of the int type limits (as defined by PHP_INT_MAX ), otherwise resolve to a float . Additionally an error of level E_WARNING is raised.
- The string is not numeric, throw a TypeError .
Behavior prior to PHP 8.0.0
Prior to PHP 8.0.0, a string was considered numeric only if it had leading whitespaces, if it had trailing whitespaces then the string was considered to be leading numeric.
- The usage of a leading numeric string would raise an E_NOTICE instead of an E_WARNING .
- If the string is not numeric, an E_WARNING was raised and the value 0 would be returned.
$foo = 1 + «10.5» ; // $foo is float (11.5)
$foo = 1 + «-1.3e3» ; // $foo is float (-1299)
$foo = 1 + «bob-1.3e3» ; // TypeError as of PHP 8.0.0, $foo is integer (1) previously
$foo = 1 + «bob3» ; // TypeError as of PHP 8.0.0, $foo is integer (1) previously
$foo = 1 + «10 Small Pigs» ; // $foo is integer (11) and an E_WARNING is raised in PHP 8.0.0, E_NOTICE previously
$foo = 4 + «10.2 Little Piggies» ; // $foo is float (14.2) and an E_WARNING is raised in PHP 8.0.0, E_NOTICE previously
$foo = «10.0 pigs » + 1 ; // $foo is float (11) and an E_WARNING is raised in PHP 8.0.0, E_NOTICE previously
$foo = «10.0 pigs » + 1.0 ; // $foo is float (11) and an E_WARNING is raised in PHP 8.0.0, E_NOTICE previously
?>
Extract Numbers From String in PHP
This approach isn’t efficient for certain use case, and simply returns the numbers present within the string together. For a more efficient, we can rely on regular expression.
Use preg_match_all() method
Use preg_match_all() method with /2+/ to extract numbers from String in PHP.
Here, output is array of matches, which can then be used to extract the numbers from the string.
We used the preg_match_all() function to search for the regular expression and extracted the numbers from the string.
We used regular expression in the form of a pattern /8+/ that matched the numbers in the string.
preg_match_all performs global regular expression match. It takes three arguments:
$pattern : The pattern to be searched
$subject : Input String
$matches :Array of all matches in the String.
Use preg_replace() method
We can achieve the same output as the filter_var method using regular expression where we replace all the characters that are not numbers with empty whitespace. The regular expression match value would be /[^0-9]/ .
Let’s illustrate this approach on the same string as in the previous section.