PHP Strings and Patterns

String Basics

hex and octal notation to display an asterisk:
echo "x2a";
echo "052";

Variable Interpolation

$who = "World";
echo "Hello $whon"; // Shows "Hello World" followed by a newline
echo ’Hello $whon’; // Shows "Hello $whon"

Variable Interpolation, cont’d

$me = ’Davey’;
$names = array (’Smith’, ’Jones’, ’Jackson’);
echo "There cannot be more than two {$me}s!";
echo "Citation: {$names[1]}[1987]";

The Heredoc Syntax

 Used to declare complex strings
 Easier to declare strings that include many double-quote characters
$who = "World";
echo <<<TEXT

So I said, "Hello $who"
TEXT;

String Length

The strlen() function is used to determine the length, in
bytes, of a string
binary-safe: all characters in the string are counted,
regardless of their value

String Transform
 The strtr() function can be used to translate certain characters of a string into other
characters
// Single character version

echo strtr (’abc’, ’a’, ’1’);

// Outputs 1bc

// Multiple-character version
$subst = array (
’1’ => ’one’,
’2’ => ’two’,

);
echo strtr (’123’, $subst);

// Outputs onetwo3

Strings as Arrays
 Individual characters of a string can be accessed as if they were members of an array
$string = ’abcdef’;
echo $string[1];

// Outputs ’b’

 Note that string character indices are zero-based - meaning that the first character of an
arbitrary string $s has an index of zero, and the last has an index of strlen($s)-1.

Comparing, Searching and
Replacing Strings

String Comparison, cont’d

$string = ’123aa’;
if ($string == 123) {
// The string equals 123

}

String Comparison
$str = "Hello World";
if (strcmp($str, "hello world") === 0) {

// We won’t get here, because of case sensitivity
}
if (strcasecmp($str, "hello world") === 0) {
// We will get here, because strcasecmp()
// is case-insensitive
}

String Comparison, cont’d

$s1 = ’abcd1234’;

$s2 = ’abcd5678’;
// Compare the first four characters
echo strncasecmp ($s1, $s2, 4);

String Search

$haystack = "abcdefg";
$needle = ’abc’;
if (strpos ($haystack, $needle) !== false) {
echo ’Found’;
}

String Search, cont’d

$haystack = ’123456123456’;
$needle = ’123’;
echo strpos ($haystack, $needle);

// outputs 0

echo strpos ($haystack, $needle, 1); // outputs 6


$haystack = ’123456’;
$needle = ’34’;
echo strstr ($haystack, $needle); // outputs 3456

Note Well

In general, strstr() is
slower than strpos()—
therefore, you should
use the latter if your only
goal is to determine
whether a certain
needle occurs inside the
haystack.
Also, note that you
cannot force strstr() to
start looking for the
needle from a given
location by passing a
third parameter.


// Case-insensitive search

echo stripos(’Hello World’, ’hello’);

// outputs zero

echo stristr(’Hello My World’, ’my’);

// outputs "My World"

// Reverse search
echo strrpos (’123123’, ’123’);

// outputs 3

Matching Against a Mask

$string = ’133445abcdef’;
$mask = ’12345’;

echo strspn ($string, $mask);

// Outputs 6

Note Well

The strcspn() function
works just like strspn(),
but uses a blacklist
approach instead—that
is, the mask is used to
specify which
characters are
disallowed, and the
function returns the
length of the initial
segment of the string
that does not contain
any of the characters
from the mask.

Matching Against a Mask, cont’d

$string = ’1abc234’;
$mask = ’abc’;

echo strspn ($string, $mask, 1, 4);

Search and Replace Operations

echo str_replace("World", "Reader", "Hello World");
echo str_ireplace("world", "Reader", "Hello World");

Search and Replace, cont’d

echo str_replace(array("Hello", "World"),
array("Bonjour", "Monde"), "Hello World");
echo str_replace(array("Hello", "World"), "Bye", "Hello
World");


echo substr_replace("Hello World", "Reader", 6);
echo substr_replace("Canned tomatoes are good",
"potatoes", 7, 8);

$user = “henry@thinktankesolutions.com";
$name = substr_replace($user, "", strpos($user,
’@’);
echo "Hello " . $name;

Extracting Substrings
$x = ’1234567’;
echo substr ($x, 0, 3);

// outputs 123

echo substr ($x, 1, 1);

// outputs 2

echo substr ($x, -2);

// outputs 67

echo substr ($x, 1);

// outputs 234567

echo substr ($x, -2, 1);

// outputs 6

Formatting Numbers

// Shows 100,001
echo number_format("100000.698");
// Shows 100 000,698
echo number_format("100000.698", 3, ",", " ");

Formatting Currency Values

setlocale(LC_MONETARY, "en_US");
echo money_format(’%.2n’, "100000.698");

//$100,000.70

setlocale(LC_MONETARY, "ja_JP.UTF-8");
echo money_format(’%.2n’, "100000.698");

//¥100,000.70

Generic Formatting
 If you are not handling numbers or currency values, you can use the printf() family of
functions to perform arbitrary formatting of a value.
 A formatting specifier always starts with a percent symbol and is followed by a type
specification token:
 A sign specifier (a plus or minus symbol) to determine how signed numbers are to be rendered
 A padding specifier that indicates what character should be used to make up the required
output length, should the input not be long enough on its own
 An alignment specifier that indicates if the output should be left or right aligned
 A numeric width specifier that indicates the minimum length of the output
 A precision specifier that indicates how many decimal digits should be dis-played for floatingpoint numbers

Commonly Used Specifiers
b

Output an integer as a Binary number.

c

Output the character which has the input integer as its ASCII value.

d

Output a signed decimal number

e

Output a number using scientific notation (e.g., 3.8e+9)

u

Output an unsigned decimal number

f

Output a locale aware float number

F

Output a non-locale aware float number

o

Output a number using its Octal representation

s

Output a string

x

Output a number as hexadecimal with lowercase letters

X

Output a number as hexadecimal with uppercase letters

Examples of printf() usage
$n = 123;
$f = 123.45;
$s = "A string";
printf ("%d", $n); // prints 123
printf ("%d", $f); // prints 123
// Prints "The string is A string"
printf ("The string is %s", $s);
// Example with precision
printf ("%3.3f", $f); // prints 123.450
// Complex formatting

function showError($msg, $line, $file)
{
return sprintf("An error occurred in %s on "line %d: %s", $file, $line, $msg);

}
showError ("Invalid deconfibulator", __LINE__, __FILE__);

Parsing Formatted Input

$data = ’123 456 789’;
$format = ’%d %d %d’;

var_dump (sscanf ($data, $format));

PHP Strings and Patterns

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