Table of Contents for

MySQL in a Nutshell, 2nd Edition

This function returns an object containing information about a field from a results set given. Information is given on the first field of a results set waiting to be returned; the function can be called repeatedly to report on each field of a SELECT statement. A number may be given as the second argument to skip one or more fields. The elements of the object are as follows: name for column name; table for table name; max_length for the maximum length of the column; not_null, which has a value of 1 if the column cannot have a NULL value; primary_key, which has a value of 1 if the column is a primary key column; unique_key, which returns 1 if it’s a unique key; multiple_key, which returns 1 if it’s not unique; numeric, which returns 1 if it’s a numeric data type; blob, which returns 1 if it’s a BLOB data type; type, which returns the data type; unsigned, which returns 1 if the column is unsigned; and zerofill, which returns 1 if it’s a zero-fill column. Here is an example:

...
$sql_stmnt = "SELECT * FROM workreq LIMIT 1";
$results = mysql_query($sql_stmnt);
$num_fields = mysql_num_fields($results);
for ($index = 0; $index < $num_fields; $index++) {
  $info = mysql_fetch_field($results, $index);
  print "$info->name  ($info->type $info->max_length) \n";
}
...

Here, all of the columns for one record are selected and placed in $results. The number of fields is determined by mysql_num_fields() for the for statement that follows. The for statement loops through each field of the results set and uses mysql_fetch_field() to return the field information in the form of an object. Then the example prints out the name of the field, the data type, and the maximum length. Here are the first few lines of the output from this script:

wr_id  (int 4)
wr_date  (date 10)
clientid  (string 4)
...