$substr
Description:
Returns the substring of text beginning with the character at the start
index, up to (but not including) the character at the end index. Indexes are
zero-based. Negative numbers will be counted back from the end of the string. If
the start index is left blank, it will default to the start of the string. If
the end index is left blank or not included, it will default to the end
of the string. If the start index evaluates to a negative
number (e.g.: text is “abc” and start is -10), it will default to the
start of the string. Similarly, if end index is a number greater than the
number of characters in the string, it will default to the end of the string.
Invalid index values (e.g.: start greater than end) will return an empty
string.
Example:
The following statements will return the values indicated:
$substr(abcdefg) ==> "abcdefg"
$substr(abcdefg,3) ==> "defg"
$substr(abcdefg,,3) ==> "abc"
$substr(abcdefg,0,3) ==> "abc"
$substr(abcdefg,-3) ==> "efg"
$substr(abcdefg,-6,3) ==> "bc"
$substr(abcdefg,-10,3) ==> "abc"
$substr(abcdefg,3,1) ==> ""