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Extractingreplacing substrings

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Single characters can be extracted using array (square brace) syntax as well as curly brace syntax. These two syntaxes will only return a single character from the string. If more than one character is needed, a function will be required, i.e.- substr

Strings, like everything in PHP, are 0-indexed. 

$foo = 'Hello world';

$foo[6]; // returns 'w'
$foo{6}; // also returns 'w'

substr($foo, 6, 1); // also returns 'w'
substr($foo, 6, 2); // returns 'wo'

Strings can also be changed one character at a time using the same square brace and curly brace syntax. Replacing more than one character requires a function, i.e.- substr_replace 

$foo = 'Hello world';

$foo[6] = 'W'; // results in $foo = 'Hello World'
$foo{6} = 'W'; // also results in $foo = 'Hello World'

substr_replace($foo, 'W', 6, 1); // also results in $foo = 'Hello World'
substr_replace($foo, 'Whi', 6, 2); // results in 'Hello Whirled'
// note that the replacement string need not be the same length as the substring replaced
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String formatting:
* String formatting
* String interpolation
* Extractingreplacing substrings
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