Programming PHP, 3rd Edition

Cleaning Strings

Often, the strings we get from files or users need to be cleaned up before we can use them. Two common problems with raw data are the presence of extraneous whitespace and incorrect capitalization (uppercase versus lowercase).

Removing Whitespace

You can remove leading or trailing whitespace with the trim(), ltrim(), and rtrim() functions:

$trimmed = trim(string [, charlist ]);
$trimmed = ltrim(string [, charlist ]);
$trimmed = rtrim(string [, charlist ]);

trim() returns a copy of string with whitespace removed from the beginning and the end. ltrim() (the l is for left) does the same, but removes whitespace only from the start of the string. rtrim() (the r is for right) removes whitespace only from the end of the string. The optional charlist argument is a string that specifies all the characters to strip. The default characters to strip are given in Table 4-3.

Table 4-3. Default characters removed by trim(), ltrim(), and rtrim()

Character	ASCII value	Meaning
" "	0x20	Space
"\t"	0x09	Tab
"\n"	0x0A	Newline (line feed)
"\r"	0x0D	Carriage return
"\0"	0x00	NUL-byte
"\x0B"	0x0B	Vertical tab

For example:

$title = "   Programming PHP  \n";
$str1 = ltrim($title);   // $str1 is "Programming PHP  \n"
$str2 = rtrim($title);   // $str2 is "   Programming PHP"
$str3 = trim($title);    // $str3 is "Programming PHP"

Given a line of tab-separated data, use the charlist argument to remove leading or trailing whitespace without deleting the tabs:

$record = "  Fred\tFlintstone\t35\tWilma\t   \n";
$record = trim($record, " \r\n\0\x0B ...