What's the difference between fgets and current? - php

Question

In the PHP manual, the SplFileObject has two methods that seem very similar:
$file->fgets()
Gets a line from the file.
$file->current()
Retrieves the current line of the file.
The documentation on procedural fgets is even closer to current():
Gets line from file pointer.
But there's no note about one being an alias of the other. Both take no parameters. What is the difference between these?

Answer 1

The real difference that matter is, e.g. we have this file
foo
bar
The below function will print foo bar
$file = new \SplFileObject("test.txt");
while (!$file->eof()) {
echo $file->fgets();
}
But this function will print foo continuously
$file = new \SplFileObject("test.txt");
while (!$file->eof()) {
echo $file->current();
}
Because fgets starts from begin and reading the next line which is the first line, then it reads the next line which is the seconds line and stops because it found end of file but current always read the current line and never goes to next line so it never breaks of the loop, you need to use next function to read next line, so the first code is equivalent with:
$file = new \SplFileObject("test.txt");
while (!$file->eof()) {
echo $file->current();
$file->next();
}
Edit: also check Josiah answer about the difference with flag and Axalix to see the source code diffrence

Answer 2

One difference is that current can function as fgetcsv or fgets depending on whether the SplFileObject::READ_CSV flag is set. The underlying implementation is almost the same (without moving the pointer, see other answers) as either, depending on that flag.
This means that current can either return a string or an array, depending on the presence of the flag.
Presumably this is done for code portability, though it seems like it would be more code than fgetcsv to accomplish the same work, and perhaps minutely less performant due to the extra logical call (see Axalix's answer).

Answer 3

There are some differences in implementation. It seems like fgets is shorter and it only does what is says Reads the line from a file
https://github.com/php/php-src/blob/4d9a1883aa764e502990488d2e8b9c978be6fbd2/ext/spl/spl_directory.c
/* {{{ proto string SplFileObject::current()
Return current line from file */
SPL_METHOD(SplFileObject, current)
{
spl_filesystem_object *intern = Z_SPLFILESYSTEM_P(getThis());
if (zend_parse_parameters_none() == FAILURE) {
return;
}
if(!intern->u.file.stream) {
zend_throw_exception_ex(spl_ce_RuntimeException, 0, "Object not initialized");
return;
}
if (!intern->u.file.current_line && Z_ISUNDEF(intern->u.file.current_zval)) {
spl_filesystem_file_read_line(getThis(), intern, 1);
}
if (intern->u.file.current_line && (!SPL_HAS_FLAG(intern->flags, SPL_FILE_OBJECT_READ_CSV) || Z_ISUNDEF(intern->u.file.current_zval))) {
RETURN_STRINGL(intern->u.file.current_line, intern->u.file.current_line_len);
} else if (!Z_ISUNDEF(intern->u.file.current_zval)) {
RETURN_ZVAL(&intern->u.file.current_zval, 1, 0);
}
RETURN_FALSE;
} /* }}} */
VS
/* {{{ proto string SplFileObject::fgets()
Rturn next line from file */
SPL_METHOD(SplFileObject, fgets)
{
spl_filesystem_object *intern = Z_SPLFILESYSTEM_P(getThis());
if (zend_parse_parameters_none() == FAILURE) {
return;
}
if(!intern->u.file.stream) {
zend_throw_exception_ex(spl_ce_RuntimeException, 0, "Object not initialized");
return;
}
if (spl_filesystem_file_read(intern, 0) == FAILURE) {
RETURN_FALSE;
}
RETURN_STRINGL(intern->u.file.current_line, intern->u.file.current_line_len);
} /* }}} */
Edit:
So the difference is in return. current (if some flags are set) may return RETURN_ZVAL (php array for this case) OR string OR. fgets returns strings or FALSE. Also if (spl_filesystem_file_read(intern, 0) == FAILURE) { which is way faster than anything else if we just want to read a line from a file w/o making any other work.