Ok..
Thanks for your reply, It makes much more sense not to need a loop as yes, it is just single dimensional.
Now, I thought dude, you've got it thanks, then in tried it and it still not finding it...
My code is now exactly as you have it (which it correct.)
Needle variable is a simple array
$conf['guild']['reqAchievements'] = array(399, 402, 406, 5350);
Print_r of $charAchievements
Array ( [0] => 6 [1] => 7 [2] => 8 [3] => 9 [4] => 10 [5] => 11 [6] => 12 [7] => 13 [8] => 42 [9] => 43 [10] => 44 [11] => 45 [12] => 46 [13] => 73 [14] => 116 [15] => 154 [16] => 162 [17] => 166 [18] => 168 [19] => 199 [20] => 201 [21] => 208 [22] => 212 [23] => 213 [24] => 214 [25] => 216 [26] => 218 [27] => 223 [28] => 227 [29] => 229 [30] => 231 [31] => 238 [32] => 245 [33] => 247 [34] => 263 [35] => 397 [36] => 398 [37] => 399 [38] => 477 [39] => 478 [40] => 479 [41] => 480 [42] => 481 [43] => 482 [44] => 483 [45] => 484 [46] => 486 [47] => 488 [48] => 500 [49] => 503 [50] => 504 [51] => 505 [52] => 506 [53] => 509 [54] => 512 [55] => 513 [56] => 515 [57] => 516 [58] => 522 [59] => 545 [60] => 556 [61] => 557 [62] => 558 [63] => 584 [64] => 587 [65] => 621 [66] => 627 [67] => 628 [68] => 629 [69] => 631 [70] => 632 [71] => 633 [72] => 634 [73] => 635 [74] => 637 [75] => 639 [76] => 642 [77] => 647 [78] => 648 [79] => 649 [80] => 650 [81] => 653 [82] => 657 [83] => 659 [84] => 666 [85] => 686 [86] => 696 [87] => 697 [88] => 699 [89] => 700 [90] => 706 [91] => 727 [92] => 728 [93] => 731 [94] => 732 [95] => 733 [96] => 734 [97] => 735 [98] => 736 [99] => 750 )