PHP MySQL - Stilson.net

www.it-ebooks.infoCHAPTER 10 • WORKING WITH THE FILE AND OPERATING SYSTEMMoving the File PointerIt’s often useful to jump around within a file, reading from and writing to various locations. Several PHPfunctions are available for doing just this.Moving the File Pointer to a Specific OffsetThe fseek() function moves the pointer to the location specified by a provided offset value. Its prototypefollows:int fseek(resource handle, int offset [, int whence])If the optional parameter whence is omitted, the position is set offset bytes from the beginning ofthe file. Otherwise, whence can be set to one of three possible values, which affect the pointer’s position:SEEK_CUR: Sets the pointer position to the current position plus offset bytes.SEEK_END: Sets the pointer position to the EOF plus offset bytes. In this case,offset must be set to a negative value.SEEK_SET: Sets the pointer position to offset bytes. This has the same effect asomitting whence.Retrieving the Current Pointer OffsetThe ftell() function retrieves the current position of the file pointer’s offset within the resource. Itsprototype follows:int ftell(resource handle)Moving the File Pointer Back to the Beginning of the FileThe rewind() function moves the file pointer back to the beginning of the resource. Its prototype follows:int rewind(resource handle)Reading Directory ContentsThe process required for reading a directory’s contents is quite similar to that involved in reading a file.This section introduces the functions available for this task and also introduces a function new to PHP 5that reads a directory’s contents into an array.Opening a Directory HandleJust as fopen() opens a file pointer to a given file, opendir() opens a directory stream specified by a path.Its prototype follows:247