String to num in php

Int s can be specified in decimal (base 10), hexadecimal (base 16), octal (base 8) or binary (base 2) notation. The negation operator can be used to denote a negative int .

To use octal notation, precede the number with a 0 (zero). As of PHP 8.1.0, octal notation can also be preceded with 0o or 0O . To use hexadecimal notation precede the number with 0x . To use binary notation precede the number with 0b .

As of PHP 7.4.0, integer literals may contain underscores ( _ ) between digits, for better readability of literals. These underscores are removed by PHP’s scanner.

Example #1 Integer literals

$a = 1234 ; // decimal number
$a = 0123 ; // octal number (equivalent to 83 decimal)
$a = 0o123 ; // octal number (as of PHP 8.1.0)
$a = 0x1A ; // hexadecimal number (equivalent to 26 decimal)
$a = 0b11111111 ; // binary number (equivalent to 255 decimal)
$a = 1_234_567 ; // decimal number (as of PHP 7.4.0)
?>

Formally, the structure for int literals is as of PHP 8.1.0 (previously, the 0o or 0O octal prefixes were not allowed, and prior to PHP 7.4.0 the underscores were not allowed):

decimal : 69*(_1+)* | 0 hexadecimal : 0[xX][0-9a-fA-F]+(_[0-9a-fA-F]+)* octal : 0[oO]?1+(_4+)* binary : 0[bB][01]+(_[01]+)* integer : decimal | hexadecimal | octal | binary

The size of an int is platform-dependent, although a maximum value of about two billion is the usual value (that’s 32 bits signed). 64-bit platforms usually have a maximum value of about 9E18. PHP does not support unsigned int s. int size can be determined using the constant PHP_INT_SIZE , maximum value using the constant PHP_INT_MAX , and minimum value using the constant PHP_INT_MIN .

Integer overflow

If PHP encounters a number beyond the bounds of the int type, it will be interpreted as a float instead. Also, an operation which results in a number beyond the bounds of the int type will return a float instead.

Example #2 Integer overflow on a 32-bit system

$large_number = 2147483647 ;
var_dump ( $large_number ); // int(2147483647)

$large_number = 2147483648 ;
var_dump ( $large_number ); // float(2147483648)

$million = 1000000 ;
$large_number = 50000 * $million ;
var_dump ( $large_number ); // float(50000000000)
?>

Example #3 Integer overflow on a 64-bit system

$large_number = 9223372036854775807 ;
var_dump ( $large_number ); // int(9223372036854775807)

$large_number = 9223372036854775808 ;
var_dump ( $large_number ); // float(9.2233720368548E+18)

$million = 1000000 ;
$large_number = 50000000000000 * $million ;
var_dump ( $large_number ); // float(5.0E+19)
?>

There is no int division operator in PHP, to achieve this use the intdiv() function. 1/2 yields the float 0.5 . The value can be cast to an int to round it towards zero, or the round() function provides finer control over rounding.

var_dump ( 25 / 7 ); // float(3.5714285714286)
var_dump ((int) ( 25 / 7 )); // int(3)
var_dump ( round ( 25 / 7 )); // float(4)
?>

Converting to integer

To explicitly convert a value to int , use either the (int) or (integer) casts. However, in most cases the cast is not needed, since a value will be automatically converted if an operator, function or control structure requires an int argument. A value can also be converted to int with the intval() function.

If a resource is converted to an int , then the result will be the unique resource number assigned to the resource by PHP at runtime.

From booleans

false will yield 0 (zero), and true will yield 1 (one).

From floating point numbers

When converting from float to int , the number will be rounded towards zero. As of PHP 8.1.0, a deprecation notice is emitted when implicitly converting a non-integral float to int which loses precision.

function foo ( $value ): int return $value ;
>

var_dump ( foo ( 8.1 )); // «Deprecated: Implicit conversion from float 8.1 to int loses precision» as of PHP 8.1.0
var_dump ( foo ( 8.1 )); // 8 prior to PHP 8.1.0
var_dump ( foo ( 8.0 )); // 8 in both cases

var_dump ((int) 8.1 ); // 8 in both cases
var_dump ( intval ( 8.1 )); // 8 in both cases
?>

If the float is beyond the boundaries of int (usually +/- 2.15e+9 = 2^31 on 32-bit platforms and +/- 9.22e+18 = 2^63 on 64-bit platforms), the result is undefined, since the float doesn’t have enough precision to give an exact int result. No warning, not even a notice will be issued when this happens!

Note:

NaN and Infinity will always be zero when cast to int .

Never cast an unknown fraction to int , as this can sometimes lead to unexpected results.

From strings

If the string is numeric or leading numeric then it will resolve to the corresponding integer value, otherwise it is converted to zero ( 0 ).

From NULL

null is always converted to zero ( 0 ).

From other types

The behaviour of converting to int is undefined for other types. Do not rely on any observed behaviour, as it can change without notice.

User Contributed Notes 19 notes

A leading zero in a numeric literal means «this is octal». But don’t be confused: a leading zero in a string does not. Thus:
$x = 0123; // 83
$y = «0123» + 0 // 123

Here are some tricks to convert from a «dotted» IP address to a LONG int, and backwards. This is very useful because accessing an IP addy in a database table is very much faster if it’s stored as a BIGINT rather than in characters.

IP to BIGINT:
$ipArr = explode ( ‘.’ , $_SERVER [ ‘REMOTE_ADDR’ ]);
$ip = $ipArr [ 0 ] * 0x1000000
+ $ipArr [ 1 ] * 0x10000
+ $ipArr [ 2 ] * 0x100
+ $ipArr [ 3 ]
;
?>

IP as BIGINT read from db back to dotted form:

Keep in mind, PHP integer operators are INTEGER — not long. Also, since there is no integer divide in PHP, we save a couple of S-L-O-W floor ()’s by doing bitshifts. We must use floor(/) for $ipArr[0] because though $ipVal is stored as a long value, $ipVal >> 24 will operate on a truncated, integer value of $ipVal! $ipVint is, however, a nice integer, so
we can enjoy the bitshifts.

$ipVal = $row [ ‘client_IP’ ];
$ipArr = array( 0 =>
floor ( $ipVal / 0x1000000 ) );
$ipVint = $ipVal -( $ipArr [ 0 ]* 0x1000000 ); // for clarity
$ipArr [ 1 ] = ( $ipVint & 0xFF0000 ) >> 16 ;
$ipArr [ 2 ] = ( $ipVint & 0xFF00 ) >> 8 ;
$ipArr [ 3 ] = $ipVint & 0xFF ;
$ipDotted = implode ( ‘.’ , $ipArr );
?>

var_dump((int) «010»); //output 10

First one is octal notation so the output is correct. But what about the when converting «010» to integer. it should be also output 8 ?
—————————————————————————
Answer :

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Casting to an integer using (int) will always cast to the default base, which is 10.

Casting a string to a number this way does not take into account the many ways of formatting an integer value in PHP (leading zero for base 8, leading «0x» for base 16, leading «0b» for base 2). It will simply look at the first characters in a string and convert them to a base 10 integer. Leading zeroes will be stripped off because they have no meaning in numerical values, so you will end up with the decimal value 10 for (int)»010″.

Converting an integer value between bases using (int)010 will take into account the various ways of formatting an integer. A leading zero like in 010 means the number is in octal notation, using (int)010 will convert it to the decimal value 8 in base 10.

This is similar to how you use 0x10 to write in hexadecimal (base 16) notation. Using (int)0x10 will convert that to the base 10 decimal value 16, whereas using (int)»0x10″ will end up with the decimal value 0: since the «x» is not a numerical value, anything after that will be ignored.

If you want to interpret the string «010» as an octal value, you need to instruct PHP to do so. intval(«010», 8) will interpret the number in base 8 instead of the default base 10, and you will end up with the decimal value 8. You could also use octdec(«010») to convert the octal string to the decimal value 8. Another option is to use base_convert(«010», 8, 10) to explicitly convert the number «010» from base 8 to base 10, however this function will return the string «8» instead of the integer 8.

Casting a string to an integer follows the same the logic used by the intval function:

Returns the integer value of var, using the specified base for the conversion (the default is base 10).
intval allows specifying a different base as the second argument, whereas a straight cast operation does not, so using (int) will always treat a string as being in base 10.

php > var_export((int) «010»);
10
php > var_export(intval(«010»));
10
php > var_export(intval(«010», 8));
8

Источник

intval

Returns the int value of value , using the specified base for the conversion (the default is base 10). intval() should not be used on objects, as doing so will emit an E_WARNING level error and return 1.

Parameters

The scalar value being converted to an integer

The base for the conversion

if string includes a «0x» (or «0X») prefix, the base is taken as 16 (hex); otherwise,
if string starts with «0», the base is taken as 8 (octal); otherwise,
the base is taken as 10 (decimal).

Return Values

The integer value of value on success, or 0 on failure. Empty arrays return 0, non-empty arrays return 1.

The maximum value depends on the system. 32 bit systems have a maximum signed integer range of -2147483648 to 2147483647. So for example on such a system, intval(‘1000000000000’) will return 2147483647. The maximum signed integer value for 64 bit systems is 9223372036854775807.

Strings will most likely return 0 although this depends on the leftmost characters of the string. The common rules of integer casting apply.

Changelog

Version	Description
8.0.0	The error level when converting from object was changed from E_NOTICE to E_WARNING .

Examples

Example #1 intval() examples

The following examples are based on a 64 bit system.

echo intval ( 42 ); // 42
echo intval ( 4.2 ); // 4
echo intval ( ’42’ ); // 42
echo intval ( ‘+42’ ); // 42
echo intval ( ‘-42’ ); // -42
echo intval ( 042 ); // 34
echo intval ( ‘042’ ); // 42
echo intval ( 1e10 ); // 10000000000
echo intval ( ‘1e10’ ); // 10000000000
echo intval ( 0x1A ); // 26
echo intval ( ‘0x1A’ ); // 0
echo intval ( ‘0x1A’ , 0 ); // 26
echo intval ( 42000000 ); // 42000000
echo intval ( 420000000000000000000 ); // -4275113695319687168
echo intval ( ‘420000000000000000000’ ); // 9223372036854775807
echo intval ( 42 , 8 ); // 42
echo intval ( ’42’ , 8 ); // 34
echo intval (array()); // 0
echo intval (array( ‘foo’ , ‘bar’ )); // 1
echo intval ( false ); // 0
echo intval ( true ); // 1
?>

Notes

Note:

The base parameter has no effect unless the value parameter is a string.

User Contributed Notes 17 notes

It seems intval is interpreting valid numeric strings differently between PHP 5.6 and 7.0 on one hand, and PHP 7.1 on the other hand.

echo intval ( ‘1e5’ );
?>

will return 1 on PHP 5.6 and PHP 7.0,
but it will return 100000 on PHP 7.1.

$n = «19.99» ;
print intval ( $n * 100 ); // prints 1998
print intval ( strval ( $n * 100 )); // prints 1999
?>

intval converts doubles to integers by truncating the fractional component of the number.

When dealing with some values, this can give odd results. Consider the following:

This will most likely print out 7, instead of the expected value of 8.

For more information, see the section on floating point numbers in the PHP manual (http://www.php.net/manual/language.types.double.php)

Also note that if you try to convert a string to an integer, the result is often 0.

However, if the leftmost character of a string looks like a valid numeric value, then PHP will keep reading the string until a character that is not valid in a number is encountered.

«101 Dalmations» will convert to 101

«$1,000,000» will convert to 0 (the 1st character is not a valid start for a number

«80,000 leagues . » will convert to 80

«1.4e98 microLenats were generated when. » will convert to 1.4e98

Also note that only decimal base numbers are recognized in strings.

«099» will convert to 99, while «0x99» will convert to 0.

One additional note on the behavior of intval. If you specify the base argument, the var argument should be a string — otherwise the base will not be applied.

print intval (77, 8); // Prints 77
print intval (’77’, 8); // Prints 63

Источник

String to num in php